All about fish glue and hide glue

Brief History

Fish glue apparently was ordinarily available in the third century, since Hippolytus notes its use by magicians and diviners on the streets of Rome, in about 220 C.E. According to Hippolytus, fish glue had asbestos like properties, since the trickster “anoints his feet with fish glue” so that he can walk over hot coals without being burned.
A translation of Dioscorides of Anazarbus from an ancient Greek text of what fish glue is made from.
“Ichthyokolla is the stomach of a whale sized fish. The best kind is made in Pontus, and it is white, rather thick, and not scaly, and melts with a low heat (very rapidly). It is useful in making plasters for the head (skull fractures) and has properties appropriate for the treatment of Leprosies and in the manufacture of lotions that erase wrinkles from the face.”
Ladies, before you go out and slap fish glue over your faces note the translation reads “used in the manufacture of lotions” so obviously, there must be other agents mixed with it.
A Caspian fisherman who is presumed to be an eye witness, accounts in the making of fish glue and it’s workings:
“they take out the guts and boil them, and make from this a glue that is very useful, since it holds all things together quite firmly, and sticks to whatever it has been attached, and dries very shiny. And it binds everything that it holds and unites, so tightly that even if it is soaked in water for up to ten days, it will not dissolve or come apart. Moreover, Ivory carvers use it and produce very beautiful pieces.”
Fish glue usually is soluble, to render it insoluble it will need to be in contact with metal ions that also applies to hide glue.

Fish glue is a transparent, colourless, water soluble glue. There are various types of fish glues. The higher quality Isinglass to the lower quality, made from the skins of non oily types of fish as well as their bones and cartilage which are sold in liquid format. The agglutinating agents are removed by extraction with hot water, then cooled and dried to produce gelatin or glue. Varied production techniques can produce poor quality fish glues.

The highest quality fish glue is Isinglass which is made from the swim air bladders of Sturgeons. Isinglass was originally made from air bladders of the great Russian Beluga Sturgeon, found in the fresh waters of the Caspian and Black seas. The Beluga is a monstrous sized fish than can live up to 113 years.

beluga

Unfortunately, due to its overfishing the Beluga has been placed on the endangered species list which has prompted many governments worldwide to place restrictions on its trade.
In 1939, restrictions were placed on Russian exports, it’s unclear to me whether these export restrictions were solely placed on the export of this fish or on all Russian exports. However due to this, other fish air bladders were used from various fish and Isinglass became a generic term used. North American Isinglass is made from Cod or Hake.
To prepare Isinglass, the air bladders are removed from the fish, cleaned and air dried. The dried bladder is then cut into thin translucent strips, these strips which are nearly 80% collagen are dissolved in hot water then diluted and cooled into flat disks. Collagen is a protein found in cartilages, tendons, bones etc. This is a very strong and soluble adhesive that can be used in low concentrations. Sturgeon glue is rarely available outside of Russia.
Genuine Isinglass fish glue costs around 578 euros/kg or 57.80 per 100 grams (3.5 ounces) Here is the link to where you can purchase genuine Isinglass fish glue https://www.dictum.com/en/surfaces/glue-accessories/natural-glues/450142/isinglass-glue-granulate

450142_01_P_WE_8-Hausenblasenleim-Granulat

Another link but more expensive:
http://shop.kremerpigments.com/en/mediums-binders-und-glues/water-soluble-binders/natural-glues-und-agglutinants/5721/parchment-glue

The purity of Isinglass can vary due to the diverse manufacturing processes, unfortunately there is no way to verify any of the processes. Germany is usually a good source for trusted companies, Milligan and Higgins in the US is definitely a trusted company for hide glue, but I don’t know if they have Isinglass as they have not yet responded to my email. Behlen, I also don’t know what type of hide glue they sell as there is a variety of low to high grade which I will go into detail later. I haven’t also located any of their products that indicate that they sell Isinglass. Lee Valley sells liquid fish glue which is of a lower grade and the one I have, I have tested it despite it being over 5 years old and has worked remarkably well. I have tried with full force to break the pieces apart and cannot do so and remember this is with a lower grade fish glue.
Fish glue is often sensitive to changes in humidity and temperature and can shrink while drying.   It doesn’t gel which means you have a long open time; some reports claim 30 mins while others claim 1.5 -2 hrs.   It also means you can work in cooler conditions without the need to warm the work prior to gluing. You also apply the glue in its cold state so there’s no heating involved like hot hide glue or liquid hide glue.
Fish glue cleans up with water well whilst still wet, but difficult to clean once its dry. You can also refrigerate it and it will last for many years, the cold prevents the bacteria from forming but also increases the viscosity, so prior to use let it sit at room temperature for about an hour for it to return to its normal viscosity.  If frozen you will render the glue useless, once in every few months shake the bottle to prolong its life.

Technical detail simplified – Bloom Strength

Bloom strength means gel strength and is measured in grams or another term is bloom grams, they could have easily picked one word. Manufacturers commonly distinguish between grades of glue by their bloom strength, which usually covers a wide range starting as low as 30g for weak bone glue, to rigorously extracted hide glues up to 500g being a very strong glue.
Gelatins extracted from cold water fish do not have specified gel strengths as they are liquid at room temperature.

Open time, tack and drying

The setting time of animal glues depends primarily on gelling temperature which is known as T gel and gel strength. The lower the T gel and gel strength, the longer the open time of the solution, another words the longer it takes for the glue to gel. High Bloom hot hide glues tend to gel rapidly as gelation occurs at comparatively high temperatures. Gelatinous glues derived from fish have a low T gel due to their chemical structure, and cold set liquid hide glues, are convenient to use when long open times are required. Commercial fish glues usually contain preservatives and, sometimes, small amounts of other additives such as colour brightener, deodorising agents or fragrance. Liquid
hide glues generally have further additives to inhibit gelation at room temperature. These are typically salts, like urea, thiourea or phenols that extend the setting time by inhibiting renaturation of the gelatinous matrix. Some manufacturers claim that their liquid hide glues does not contain gelling inhibitors in which case the gelatinous matrix must be considerably affected by molecular cleavage, and it’s not the hollow between a woman’s breast.   Molecular cleavage means molecular separation to achieve the comparatively low molecular weight that is necessary for the glue to be in a liquid state.
In general, glues of higher bloom strength develop tack faster than lower bloom glues.
The tack strength of glues can be tested between the two finger tips.

testing

Isinglass solutions may appear to be less tacky than equivalent concentrations of hide glue, as they take longer to set at room temperature since their lower gelation temperature delays the development of tack.
Drying times depends upon the ambient temperature and relative humidity. Glues dry by evaporation of water however; the drying times can be increased raising the room temperature. It is recommended that these adhesives be allowed to dry as slowly as possible to maximise the elasticity and strength or should I say toughness of the glue film.
Isinglass naturally develops highly stable and elastic films if dried at room temperature, being slightly above its temperature gel. It’s interesting to note if I may back track a little, that heating these glues at high temperatures say 80c or 90c would result in only small amount of loss of strength if only done for a few minutes, anymore would render the glue useless.
Viscosity meaning thickness is an important factor in the choice of adhesive for bonding or consolidation, as it will affect the degree of penetration into a substrate. If the viscosity is too low the glue may penetrate too far into the wood, leaving the joint starved of adhesive. For consolidation of porous materials, high viscosity may prevent adequate penetration and cause stress to develop at the interface between consolidated and unconsolidated areas.
Isinglass has a much higher viscosity than hide glue, in order to obtain glue solutions of low viscosity it is not always advisable to over dilute high bloom glues excessively, hide glue is a high bloom glue. If you did so, you would weaken its strength, leeching, swelling and staining the wood may result if it is water sensitive. In this case, a lower gel strength glue would be preferable. Slow gelation and lower viscosity promote uniform film formation as glue is able to spread evenly, providing adequate wetting of the surface, then again using a larger natural bristle brush will achieve the same result.
BR-010-2
Hide glues generally have greater cohesive strength than bone glues which display a lower tensile strength and are much more brittle.
The tensile strength of hide glues is typically around 39 megapascals (MPa) (5700 psi) A tensile strength is the maximum strength that can be applied to it before it breaks, that’s pretty darn strong in my books. Cold water fish gelatins show a comparatively low tensile strength of around 22MPa (3200 psi) which again is very bloody strong. A high tensile strength similar to that of hide glue has been reported for mildly prepared Isinglass from Sturgeon, making it a useful adhesive for bonding wooden joints. Literature confirms that Isinglass has often been used for structural woodwork in the far east, to me that’s impressive.
Although Rabbit skin glue has a high gel strength, it has been stated as having a lower cohesion and bonding strength than other hide glues. This is thought to be due to its high fat content. So stay away from McDonalds.

Creep and Elasticity

Isinglass has more elasticity than hide glue. Glue recipes often contain additives such as sugar alcohols (glycerine, sorbitol) and polysaccharides (dextrins) to improve elasticity and toughness. One traditional method for achieving elastic and resilient glue films is in the addition of honey. Sugars are hygroscopic, by adding water you induce gel strength and viscosity. These additives are known as plasticisers even though they don’t actually plasticise the glue. High proportion of fat also improves the elasticity but at the cost of reducing final bond and gel strength. A high water content or an excess of hygroscopic additives like sugar, can promote an unwanted tendency to creep.

Resolubility (Reversibility)

Animal glues are well known for their resolubility or better known as reversibility, but it can be rendered insoluble if it comes in contact with metal ions e.g. Metal foils, tools, pigments), or with certain organic pigments and tannins, either before, during or even after their application. A pigment is a colourant but so is a dye, the difference between the two is that a pigment is insoluble, while a dye isn’t because it’s a liquid. Cold liquid hide and fish glues, the ingredients of which are unknown to the supplier and end user, may already contain additives that promote cross linking and, therefore, increase insolubility. I have read many reports of users claiming they had extreme difficulties pulling instruments apart for repairs. This is why I cannot stress this point enough, to always buy from a trusted source like Milligan and Higgins. I’ve never used hide glue from anyone else and therefore I cannot vouch for them but I would never buy the cheap ones offered on eBay as you just don’t know who manufactured them. There has been a lot of rave about Behlen hide glue, I don’t know because I’ve never bothered to investigate. It’s a German company and Germany is well known for quality products.

Hide Glue Preparation

Liquid Hide OBG – Heat in bottle up to 140°F (60°c)

Hot Hide Glue – Measure weight by volume of water, take how much you’re going to need and place it in a plastic or glass container NOT METAL then fill with cold water just to cover the granules and leave uncovered for half hour or best 24 hours. Heat gluepot to 140°F and cook your glue. Stir occasionally, to thin it add hot water equalling the temperature of the glue. Do not over thin it and don’t let it be too thick, if it’s thick it will gel quicker resulting in a poor bond. Clamping time minimum 12hrs best 24hrs Reactivate with heat and water.

Liquid Fish Glue – Use in a cold state (no heating required) Clamp for minimum 12 hours, best 24hrs. Cleans up with water best when glue is still wet. Reactivate with water

Isinglass (Highest Quality Fish Glue)
This is an extract from Alba Art Conservation

STEP BY STEP: HOW TO MAKE GLUE FROM FISH BLADDERS

Part of the routine activities of conservators is to make our own tools and solutions for use in conservation treatment. Many traditional materials can be found on specialty websites and in stores, but some we just prefer to mix ourselves. Isinglass is a natural and refined glue made from gelatin from cooked down sturgeon bladders. It’s optical properties, such as reversibility, aging characteristics, and strength, make it a very good choice of glue to be used in many conservation treatment applications. It is used mainly in consolidation (stabilization of flaking media), though also has applications in tear repair, facing, and as a general adhesive. I hope this blog post illustrates the care and time conservators put into selecting (and making) their materials, as well as the actual treatment of art.

First, the swim bladders of the sturgeon are purchased dried and unprocessed. They should be free of blood clots and other large inclusions.  For this project, I used 50 grams of dried Salianski bladders purchased from L. Cornelissen & Son.

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The swim bladders should be soaked overnight in water using approximately a 1:10 glue-to-water ratio.  I eye-balled the ratio in a large glass beaker to a final volume of about 800 ml. To help them absorb water, the bladders can be cut into smaller pieces. I found this time-consuming and difficult, so I ended up soaking them whole. After a period of 24 hours, the bladders should be spongy to the touch and able to be easily pulled apart.

Once the bladders are sufficiently spongy, they should be kneaded into a homogeneous blob. The texture was kind of doughy at this point, and obtaining the blob was easier than I thought. Any hard bits should be worked into the dough. If there are a few remaining, they will be filtered out at a later stage. download (1)

The glue and water were placed in a makeshift double boiler using the glass beaker, a wooden block, and a large cooking pot.  The mixture should be cooked in hot water, never exceeding 140 degrees F (60 degrees C). I allowed the glass beaker to come to temperature in the water and kept a digital thermometer in the cooking water to monitor the water temperature. To double check, I also kept a meat thermometer inserted in the water and had a glass of cold water on hand to cool the water, if necessary. As the water began to reach temperature, the mixture became cloudy as the dough began to dissolve.  The solution was stirred with regularity and after about 45 minutes, the glue was mostly in solution. I found that I had to get the outside water temperature very close to 140 for the majority of the mixture to dissolve. The water eventually became more clear as the dough melted. To see that all was well, I checked the tack of the glue as it neared completion, and the results were satisfactory.

After cooking, the solution was filtered into a large glass jar through a nylon stocking. The material remaining in the stocking should be squeezed through to help dissolve any remaining bits. This solution was then re-filtered using the same stocking.  Bits remaining after the second filtration can be discarded with the stocking. At this point, the solution should be yellowish and clear of bits.  I poured it onto a sheet of non-stick Mylar that had been previously prepared over a large table.  Incidentally, I also had to prepare an additional sheet of Mylar to accommodate the large amount of glue produced. The glue should be left undisturbed to dry. To make more homogeneous and complete sheets, I attempted to spread the glue mid-drying with a piece of stiff Mylar with some success. I did end up getting areas of pooling that took longer to dry than others.

Once the sheet is sufficiently dried, they can be easily separated from the Mylar and cut up into smaller pieces to be stored for later use.

The cut up pieces can be stored in jars and re-dissolved in water as they are needed.  Though lengthy, the preparation of the glue yielded enough dried glue to last for a few years.  The product is very refined and sure to contain no additional additives, bulking agents, or colorants.

For the instruction on the preparation of isinglass, I would like to give credit to my graduate painting conservation professor James Hamm at Buffalo State College and to Jill Whitten and Rob Proctor.

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Qualitatively ranked comparative overview of each protein glue

I have included a table you can download. It a comparative overview of each glue

protein glue table

I think I have covered many useful topics and you should now have a solid understanding of the various types of animal protein glue without the unnecessary glossy scientific details which I have omitted, as it does not benefit us the woodworker in knowing it.  As for the contradictory data for Isinglass from sturgeon, one test from Pryzybylo indicated that the glue was resoluble in water after both tests of natural and artificial ageing was conducted. However, another report from Michel et al. indicated that their artificially aged sturgeon isinglass was insoluble in water. As you can see these are contradictory results which may be due to different preparation procedures, light source, exposure time, temperature etc. In reference to the Caspian Sea fisherman on his eye witness accounts of where the object was soaked in water for up to ten days and did not come apart is in line with Michel’s findings, but just what preparation did the ancients use to render this glue insoluble is unknown.
Animal protein glues has many uses in all fields of many trades but there is no one particular glue that you can generalise as a general glue type. Each glue has its pros and cons and each glue will perform different tasks. As an example, you cannot use hide glue for bonding metal to wood but instead you would use Fish glue, but the same glue wouldn’t suffice for gilding, instead you would use rabbit skin glue. So, as you can see they all work differently to each other, so it’s up to you as a craftsman to understand what your glue can or cannot do, and to use the appropriate glue for the job on hand.
I think by now with how much I have written on this subject not only in this article but in all my previous ones that animal protein glues, is my go to glue.

Tips

If you are experiencing problems with your glue losing its bond as I have read on many forums from Luthiers, you need to ask yourself what quality of glue are you using. Is it from a reputable source? Very high humidity can also be the cause due to high levels of moisture in the air, dry heat is not the cause. As you know by now that Fish glue is high in viscosity, by thinning the glue you’re basically starving the joint. What little glue is on there holding your piece together will come apart in even slight humid conditions. Another factor at play is people using hair dryers to force the drying times, fish glue works best when its left to dry slowly and naturally. If your workshop is in a damp environment then don’t expect much results with any animal protein glue, if your wife’s dryer is in your workshop, your shop including all your tools and wood will be soaked. Look at your environment before you blame the glue doing what it’s supposed to do.
Your customers also need to be made aware of potential mishaps and how to avoid them. All in all, in all my years of using hide glue and this fish glue is the first for me, nothing has come apart, and conditions in my area in summer are extreme, soggy high humidity. I have also just used fish glue instead of epoxy to fill in a crack in a knot on my recently bought bowsaw, it worked wonderfully and as you know this fish glue is very old and I’m confident it hasn’t gone off. Equally it’s the lower grade one from Lee Valley not the high grade Isinglass. It’s also been several days probably a week since I glued to sample together, still its impossible to break it apart. I will give it a test in the laundry when my wife uses the dryer next, just to see if it will come apart and that will the most extreme conditions.
If you’ve read this far then congratulations are in order, this length of post isn’t the norm for blogs but I do hope I will make a regular habit of it.
Take care

Fish Glue

I hate watching television even though I have two TV’s in my house but thankfully never used, I can’t stand listening to the news because there’s never anything positive to hear but they’re usual over dramatization and fear mongering tactics.  I hate politicians, because they never keep their election promises, constantly lie, they live in the back pockets of corporations, they pretend as if they know what they’re doing and they just can’t seem get along without resorting to some kind of war.  Oh, and they’re radicals because they’re ignorant.  A professor at Griffith University at the school of law once said “Ignorance breeds radicalism.”

So, I turn to books and articles written by prominent highly educated and respected people on various subjects pertaining to my interests.  I was recently doing some research on hide glue and it’s uses and made some amazingly new discoveries which could have helped me during my build of the small router plane.  Prior to the build, I was blinded to this information but a few days after the second build I make this discovery.

Did you know that metal expands and contracts with humidity and temperature fluctuations in opposite direction to the wood?  In fact, so does water.

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Did you also know that epoxy is brittle and the metal glued to wood would eventually break off?  Just when this will occur is anyone’s guess, but since I’m all about quality workmanship and having my builds outlive a generation or two at the very least, why take the risk.  I’m sure you feel the same.

Prior to knowing these facts about metal’s movement during these environmental fluctuations I was stumped on understanding why epoxies brittleness would eventually cause bond failure. Well now it all makes sense, this important bit of information I wasn’t made privy to all makes good sense, “movement”.

As woodworkers, we expect for wood to move and we make accommodations for that movement but how many of us knew that metal moves as well and in the opposite direction to wood. So, scientists came up with a solution of gluing metal to wood and that’s Loctite 330 and there are other numbered Loctite’s that will also do the same trick but, wait a minute. Isn’t antique furniture covered in brass ornaments, doesn’t some antique braces have brass plates fixed to them, ok fair enough they’re reinforced with screws but what about antique clocks and their brass fittings.


So, if these metal fixtures were glued to the wood hundred of years ago and are still affixed firmly in place today, what did they use? I’m sure Loctite didn’t exist in that era, well the answer is animal glue and fish glue to be precise.  According to Patrick Edwards fish glue was used in marquetry to glue ivory, bone, horn shell and metal (brass). Which makes perfectly good sense because all animal glues allow a certain amount of movement of these elements.

There are a variety of traditional animal glue applications that continue to be used by modern craftsmen. Rabbit skin glue is necessary for laying gold leaf properly.  Instrument makers and restorers have a wide variety of applications that depend on animal glues. For example, the fact that these glues can be coloured and mixed with many components allows the addition of plaster of Paris to glue for laying ivory keys. Marquetry workers add different colours to the glue to restore Boulle tortoise shell and make mastic. Fish glue has properties which make it perfect for exotic materials, such as tortoise shell, horn, leather, shark skin, cloth and metals. Fish glue is a liquid glue with strong cold tack grip, and its used to glue brass, pewter and copper in Boulle marquetry is further strengthened when the metal is first rubbed with a fresh clove of garlic. Animal bone and hide glues are used individually and mixed together for all types of woodworking. Diluted glues are used for veneer sizing and flattening, as well as for sizing end grain and porous woods before sanding.
Had I known these facts before I would have used fish glue and come to think of it I actually have a bottle I bought a number of years ago, I doubt very much if it’s of any use anymore in fact I just opened it for the first time and took a whiff and it stinks, but I’ll glue some small pieces with it just for fun to see if it will work being so old as it is. Having said that, Fish glue will still be good for a number of years even though it is a protein glue and fish glue is smelly by nature anyway, so the stench of mine is probably normal.
You have to admit the benefits of using animal glues far outweigh the benefits over synthetic glues, yes, it’s true there’s no ease of use.  It’s time consuming to prepare and you have to keep an eye on it constantly so it doesn’t over cook, if you’re working in a fully-fledged business production run workshop your glue must be hot and ready for use throughout the day. But, that’s life and that’s how it’s always been for the last 8000 years with this glue.
Here’s one more tip you also probably didn’t know. Cold water is added to dry glue and hot water equalling the temperature of the hot glue is added to thin it. Cold for cold and hot for hot and yet I see on YouTube cold water added to hot hide glue. If you’re going to use cold water then allow the glue to heat up to 140° F (60°C) before you use it, don’t do what I’ve seen people do and use it straight away and it’s not just on YouTube but in a particular book as well.  If I mention which book then the author/seller will get all snotty with me, funny though I must be the only one that will cop it in the chin when I get it wrong, I learn from it and move on but when it comes to them they hold a grudge and take it with them to their graves.  This is called online woodworking politics and there is a lot of that.

Take care

Drawknife

I’ve spoilt myself rotten, I bought a brand new drawknife from woodjoy tools, the blade is 8″ long he didn’t have his usual one in stock but he said he does have one fresh from the blacksmith so I took it.  I won’t say how much I paid for it but all I can say the conversion rate was a killer.

After 3 weeks wait time it finally arrived and needed sharpening badly, I knew I was in for one hell of a ride.  I started this morning at 9 am sharp and finished at 7pm, yes you read that right 10 hours of solid sharpening.  My finger are sore but I did it, I told you it was blunt real blunt and there was a whole hunk of metal to go through.  If I ever wanted a belt sander this day would of been it.  All I needed was to get to the burr stage and the rest would of been over with quickly but being as blunt as it and working the entire bevel it took all day.  I could of just made a secondary bevel but that secondary bevel would of grown with successive sharpenings so I thought just do it right the first time and be done with it.

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It’s sharp and I mean meanly sharp, when I did the thumbnail test it didn’t catch as it usually does but sliced it upon touch.  WOW I couldn’t believe I took it to such a level I honestly never sharpened anything to reach that level of sharpness before, my nail just touched it and sliced a layer off.  Call me insane 10 hours of sharpening talk about torture but just goes to show with dedication you can achieve anything.

I put it through a test drive and it just purred through the wood, now all I need to do is just practise with it to control my cuts.  To use it you skew the blade and take slicing cuts, but being so sharp whether I skewed it or not made no difference to the quality of the cut.  To take a deeper shave you tilt the blade down and up for a light cut, you can also work with it bevel down.

This is a wonderful addition to my array of tools and hopefully will see plenty of use.

Clamping

by R. Bruce Hoadley

The object of clamping a joint is to press the glue line into a continuous, uniformly thin film, and to bring the wood surfaces into intimate contact with the glue and hold them undisturbed until setting or cure is complete. Since loss of solvent causes some glue shrinkage, an internal stress often develops in the glue line during setting. This stress becomes intolerably high if glue lines are too thick. Glue lines should be not more than a few thousandths of an inch thick.

If mating surfaces were perfect in terms of machining and spread, pressure wouldn’t ‘ t be necessary. The ” rubbed joint, ” skilfully done, attests to this. But unevenness of spread and irregularity of surface usually requires considerable external force to press properly. The novice commonly blunders on pressure, both in magnitude and uniformity.  Clamping pressure should be adjusted according to the density of the wood. For domestic species with a specific gravity of O. 3 to 0. 7, pressures should range from 100 psi to 250 psi. Denser tropical species may require up to 300 psi. In bonding composites, the required pressure should be determined by the lowest-density layer. In gluing woods with a specific gravity of about 0. 6, such as maple or birch, 200 psi is appropriate. Thus, gluing up one square foot of maple requires pressure of (1 2 in. x 12 in. x 200 psi) 2 8, 800 pounds.  Over 14 tons! This would require, for an optimal glue line, 1 5 or 20 cee-clamps, or about 5 0 quick-set clamps.

Conversely, the most powerful cee-clamp can press only 10 or 1 1 square inches of glue line in maple. Jackscrews and hydraulic presses can apply loads measured in tons. But since clamping pressure in the small shop is commonly on the low side, one can see the importance of good machining and uniform spread.  But pressure can be overdone, too. Especially with low-viscosity adhesives and porous woods. too much pressure may force too much adhesive into the cell structure of the wood or out at the edges, resulting in an insufficient amount remaining at the glue line, a condition termed a starved joint. Some squeeze-out is normal at the edges of an assembly.  However, if spread is well controlled, excessive squeeze-out indicates too much pressure; if pressure is well controlled, undue squeeze-out suggests too much glue. Successful glue joints depend on the right correlation of glue consistency and clamping pressure. Excessive pressure is no substitute for good machining. Panels pressed at lower pressures have less tendency to warp than those pressed at higher pressures. Additionally, excessive gluing pressure will cause extreme compression of the wood structure.

When pressure is released, the cells spring back and add an extra component of stress to the glue line.

The second troublesome aspect of clamping is uniformity, usually a version of what I call ” the sponge effect. ” Lay a sponge on a table and press it down in the centre; note how the edges lift up. Similarly, the force of one clamp located in the middle of a flat board will not be evenly transmitted to its edges.   It is therefore essential to use heavy wooden cover boards or rigid metal cauls to ensure proper distribution of pressure.

clampin-1

 

Clamp time must be long enough to allow the glue to set well enough so that the joint will not be disturbed by clamp removal. Full cure time, that is, for development of full bond strength, is considerably longer. If the joint will be under immediate stress, the clamp time should be extended. Manufacturer’ s specified clamp times are established for optimum or recommended shelf life, temperature, wood moisture content, etc… If any of these factors is less than optimum, cure rate may be prolonged. It’s best to leave assemblies overnight.

Most glue specifications are based on ” room temperature” (70 · F). Shelf life is shortened by storage at above-normal temperature, but may be extended by cold storage. Normal working life of three to four hours at 70· F may be reduced to less than one hour at 90· F. Closed assembly at 90· F is 20 minutes, against 50 minutes at 70· F. A curing period of 10 hours at 70· F can be accelerated to 3 – 1 / 2 hours by heating to 90· F.

Finally, cured joints need conditioning periods to allow moisture added at the glue line to be distributed evenly through the wood.  Ignoring this can result in sunken joints.

When edge-gluing pieces to make panels, moisture is added to the glue lines (1), especially at the panel surfaces where squeeze-out contributes extra moisture. clamping-2If the panel is surfaced while the glue line is still swollen (2, 3), when the moisture is finally distributed the glue line will shrink (4), leaving the sunken joint effect.

Rubbed joints its success and failure

As sprung joints are great for clamping two edged boards together to make a panel, they are disastrous for non clamped rubbed joints. To avoid following the footsteps of magazine articles, I will not go into detail of what a rubbed or sprung joints are.  I believe that you are well passed the novice stage and I don’t feel it would be beneficial in re reading something you already know,  but would rather bring to your attention to something you may not have been aware of or unintentionally overlooked.

There has been a strong emphasis awarded to sprung joints, many articles and videos have been written and produced stressing the benefits of such a joint. While I don’t disagree with them, sometimes the obvious tends to skip us and we continue to apply a certain technique that has been drummed into our heads by an almost hypnotic suggestion through the continual parroting of others, that would lead to disastrous results if we were to apply the same technique using a different application. This issue I feel needs not be overlooked, but addressed in any future articles written on the subject.

The success of a rubbed joint is comprised of only two things, glue and two perfectly straight no gapped edges. A sprung joint as you know has a 32nd hollow in the middle, creating a successful rubbed joint would not be possible. The other point is the type of glue that best suit a rubbed joint would be hide glue. True, you could get away with small thin pieces using ordinary PVA or other quick setting PVA glue, but for a small cabinet or bedside table or even a coffee table, only hide glue in my opinion would be better suited for a such an application ie. rubbed joint.  I have written in my previous posts on the benefits of hide glue so I won’t go into any great depth on the subject here, other than to add, only hide glue as far as I know, has the capabilities of drawing two mating edges together as it dries, forming a good solid join and for that to happen there cannot be any gaps.

Blotch free staining update

I’m jumping the gun a little on this one but I just couldn’t hold out on it.

If you remember I did a post on this topic a few months ago, I was very excited about my discovery then and I’m even more excited about it now.  I have discovered something that actually works, even though I have only tried it on Pine I strongly believe this will work on other timbers that are prone to blotch.

I have made 2 videos on this topic and have demonstrated the steps I took to produce a blotch free stain and have made a comparative look between Minwax oil based against my own version.

I hope you find these videos most informative and helpful but before you watch these videos take a look at the samples and see for yourselves just how well this works.

The stain above I used oak.  Now have a look at the bottom pics.  The one on the left is my homemade brew and the one on the right is Minwax oil based stain.

As you can see the picture on the left shows no blotch, while the picture on the right shows heavy blotching.  What’s more remarkable is how the end grain on the left shows a uniform colour, while the minwax version shows a typical dark burnt like effect.

I usually don’t like to talk on camera because of the little amount of work I actually get done.  However, I made this exception for you today as I didn’t rehearse this and wasn’t sure if it was actually going to work with dry non resinous timber.  So I wanted all of us to find out together if it passe or failed.

Let me know what you think.

 

A good sawbench

I used to use a saw horse for all my rip and crosscutting, but a single saw horse isn’t just wide enough to support your material.   So the choice was to make one more, but that also posed some problems.  I have to kneel on the board which meant thinner boards would bend under my weight and the clutter of it eating my shop space didn’t sit well with me either.  There just had to be a better sawbench and so I devoured the net for ideas.

I looked at Chris Schwarz saw bench, then Shannon Rodgers bench and finally at Tom Fidgen sawbench.  Well that definitely was a winner for me, the bench stood 20 1/4″ x 12 7/8″ wide with a split top and 35″ long.  I like the idea of a split top, it meant that I can safely rip not so wide material.  It has dog holes for clamping and a fence for crosscutting. I made holes on both sides so the fence can be used on either side.  What I also like about this design is that one side legs are splayed and the other is square.  What this means is that you can use the square side as a reference while ripping while the splayed side provides great support to stop the bench from tipping.

It was a no brainer so I ordered his book “Hand crafted Project for the home and workshop” this book is great as it has so many other beautiful projects and none of which I ever got around to building and I bought this book probably about 2 or more years ago. Hopefully this will change as work outside my hobby always seems to get in the way.

As I was today continuing with the build of the planter box I thought it would be great if I showed you just how fast ripping with a handsaw can be.  This video isn’t sped up and no edits has been done to it, there’s nothing to sugar coat hand tooling is what it is.  It can be fast or slow it all depends on you, you are the machine, the driving force behind the tool.

The saw I’m using is a Disston 28″ 4 1/2 point  with hooked teeth.  This type of saw is mainly used for carpentry and works well slightly damped wood.  The timber I’m ripping is Radiata pine 3/4″ thick.  True not very thick stuff so ripping is made easier plus it being Radiata and not hoop pine also makes ripping easier but none the less whatever material your ripping,  your stamina and muscle strength is something you’re going to greatly rely on.

In the first video this is the full rip and in the second video I’m ripping probably  just proud of a 1/16″ from the line.  You can see as I got very near to the end I used my foot to clamp down onto the work.  Not sure if this is correct but it works for me.

Btw today was scorcher, sweat poured out of me like a running tap and sadly it landed on the sole of my LN hand plane and immediately rust formed on it.  It broke my heart.