Modern furniture manufacturing

WRITTEN BY Charles Harold Hayward

Materials

Modern methods of furniture construction are largely based on the availability of man-made materials such as reliable plywood, laminated board, chipboard, and hardboard as distinct from natural solid wood. It is not merely that manufacturers prefer the one to the other but rather that these substances are free from the great drawback fundamental to wood—movement. Natural wood shrinks as it dries or swells as it absorbs moisture from an atmosphere more humid than itself, and this movement must be allowed for in the method of construction. Unless this is done troubles may arise: splits along the grain or open joints on the one hand or jammed drawers or doors on the other. Over the years cabinetmakers have worked out ingenious systems to avoid these troubles in the use of solid wood, but today made-up materials may be regarded as inert if of good quality. To an extent solid wood has still to be used, notably for items that have to be turned, cut to shape, or moulded, and for lippings to conceal the edges of manufactured boards; but virtually everything in the form of flat panels is made up.

Natural wood

The increase in the demand for reasonably priced furniture has placed a premium on the economical use of wood. Natural wood is extremely wasteful as a material. Hardly more than 25 percent of the natural substance of a tree actually goes into the furniture made of solid wood. When account is taken of the loss in sawdust in conversion from the tree trunk (taking off the outer slab portions and sapwood) and the further loss in bringing the lumber to usable size in the workshop (the offcuts, waste in sawing shapes, in turning, in planing, cutting joints, and final cleaning up), it becomes evident that much more wood is wasted than used.

Plywood

In making plywood, the veneers are peeled rotary fashion from the log by a long knife fitted to a lathe like machine. The resulting veneer can be of unlimited width to be cut up as required. There is no loss in sawdust, and the peeling is continued until only a pole like centre is left. Much the same applies to laminated board in which both the core material and the outer plies are peeled. In the case of chipboard the timber is merely regarded as raw material to be reduced to fine chips that are dried, compressed, and assembled into boards, with resin glue as an adhesive. Where a natural wood grain is desired, a veneer is flat sliced from a flitch (longitudinal section) selected for the beauty of its grain.

Certain materials, notably chipboard, must be machined, because trimming at the edges by hand almost always shows as a deterioration. It cannot be planed; the plane merely forms dust rather than taking shavings and, owing to the abrasive nature of the material, the edge of the cutter is quickly lost. Consequently, when a panel of a certain size is required, it needs to be machine sawed to size, no further trimming being needed. This is only practicable with a precision saw capable of fine adjustment. Furthermore it requires a saw blade having tungsten teeth to resist abrasion. The same applies to any plywood or laminated board assembled with resin glue.

Another influence on the construction of furniture is the introduction of new types of adhesives in place of the traditional animal glue. Many are highly water resistant, some waterproof. Some can be applied cold, avoiding the complication of heating joints before assembly. They can be cured by heat in a matter of minutes, leaving presses and other apparatus free for other work.

Other materials

Although wood has always been regarded as the traditional material for furniture making, several other materials are now used, either entirely replacing wood or combined with it. Plastic laminate, widely used for table and other tops, is obtainable in various colours and designs and in photographically reproduced natural wood grain. Its advantages are that it resists all liquid stains, is largely heat proof against burn marks, is mark free, and is easily wiped clean. It is laid as a form of veneer on any of the man-made materials—multiply, laminated board, or chipboard, usually with a contact adhesive. As a plastic edging is needed that must be applied before the main top is put down, an essential machine tool is the portable router with veneer-trimming unit. It trims the overlapping edges of the main plastic panel without cutting into the edging.

Metal is also used to some extent, particularly for the stands and legs of furniture. Iron is generally preferred, the parts joined by welding.

Finishes too have been revolutionized. French polish, the traditional finish of the Victorian period, and indeed up to the 1930s, has been largely replaced by gloss or eggshell lacquers, which are sprayed on and are heat and water resistant and are so hard as to be practically mark free.

Upholstery and covers

Upholstery and covers are used on furniture designed for sitting or lying on. From the East, Europeans learned the use of wickerwork, which provided a ventilated and resilient background for loose cushions. The upholstered chair is a genuinely European phenomenon that achieved its most distinguished and logical form in England during the 18th century. Poor heating systems in houses, general prosperity, and a desire for comfort were the conditions that gave rise to a number of imaginatively varied types of upholstered armchairs in which the only wood visible is in the legs, with the back closing right up against the sitter and side wings affording protection from inevitable drafts.

Wicker Chair

The upholstered chair created a new effect that depended almost entirely upon the craftsmanship of the upholsterer. The upholstered chair or sofa has remained a specialty of the Anglo-Saxon world; club life in particular contributed to its popularity and resulted in heavily stuffed forms including that of the so-called chesterfield.

By mid-20th century, new materials such as foam rubber and various types of plastic composition had inspired independent methods that dispensed entirely with traditional upholstery techniques. Upholstery was succeeded by moulded plastic forms and by sacks filled with plastic balls that are able to conform to the changing positions of the body.

Upholstery, materials used in the craft of covering, padding, and stuffing seating and bedding. The earliest upholsterers, from early Egyptian times to the beginning of the Renaissance, nailed animal skins or dressed leather across a rigid framework. They slowly developed the craft to include cushions, padding, and pillows—stuffed with such materials as goose down and horsehair.

The medieval upholsterer, who was primarily concerned with fabrics, made mattresses and hangings. In the 17th century beds were draped with sumptuous fabrics and ornate trimmings; as these beddings became less fashionable, chairs and sofas were in turn elaborately upholstered with velvet, silks, and needlework.

Springs, which permitted soft, bulky shapes, were first used by upholsterers in the 18th century; helical by the mid-19th century, they were later flattened for maximum resiliency. Upholstery techniques were revolutionized in the 20th century with the introduction of moulded sponge rubber, dirt and liquid retardants, plywood, Naugahyde, and synthetic fibres, which created new springing, cushioning, and covering materials.

Inlay and marquetry

Inlaid woodwork, in which decorative material such as wood or ivory is set into the surface of the veneer, has accompanied the art of furniture making for thousands of years. Ivory inlay can be seen in Egyptian furniture, particularly in small, meticulously executed toilet caskets, but it is difficult to locate in Greek and Roman furniture, today known almost exclusively from pictorial representations.

In medieval Europe, inlay work gave way to wood carving and then experienced a rich period of development during the Renaissance in Italy. Italian intarsia (mosaic of wood) work found particular favour in panels over the backs of choir stalls and in the private studies and chapels, or oratories, of princes. An intarsia study of the Duke of Urbino, an Italian nobleman and patron of the arts, is still preserved in the palace of Urbino, and a corresponding room, originally at Gubbio, is now in the Metropolitan Museum of Art in New York. Together with illusionism, linear perspective (the technique of representing on a plane or curved surface the spatial relation of objects as they might appear to the eye), which had just been discovered, achieved triumphs in Italian intarsia work.

Ivory was used on both Renaissance and Baroque cupboards, sparingly to begin with, lavishly later on. Inlay work was especially used in the many splendid German and French cabinets of the period. In the Netherlands and England an extremely rich form of marquetry (patterns formed by the insertion of pieces of wood, shell, ivory, or metal into the wood veneer) was developed, incorporating floral motifs in various kinds of exotic wood on walnut. English grandfather clocks made around 1700 often had richly inlaid cases. It was in France, however, during the Rococo period especially that inlay work reached unprecedented levels of quality. The serpentine sides and fronts of commodes were veneered with costly woods whose often relatively simple grain patterns formed an effective background for richly ornamented mounts of gilded bronze.

Quran Stand Book Holder

Quran stands are a necessity for Muslims, with the utmost importance of reading the Quran with correct postures. The Quran Book Stand Holder is a beautiful Moroccan design that suits any home décor. The holder has a generous sized top, perfect for reading the Qur’an in its entirety. The legs are cut into a decorative serpentine shape typical of Morocco furniture with another added beautiful decorative feature of scrolled flowers. This stand is made entirely by hand. The finish used is an all natural non-toxic finish that gives it an antique, rustic, attractive look.

The Quran Book Stand Holder measures 19″ x 11 1/4″ x 15″ or 482 x 285 x 381mm

Price AU$70 plus shipping.

For international shipping please email for actual shipping quote.

Hide Glue – New Information Part VII

DRY MIX RATIO/DENSITY OF HIDE GLUE

Some practical hints and helps:

The following weights and measures are approximate and intended to give some basic guidelines for preparing hide glue without using sophisticated equipment.

1 cup of dry glue weighs 5 ½ ounces (155-160 grams)

¾ cup of water weighs 5 ½ ounces

2 ½ tablespoons of Urea Prills weighs 1 ounce

1 ½ tablespoons of salt weighs 1 ounce

To prepare various glue solutions use:

            1 cup glue to ¾ cup water for 1 – 1.  

            1 cup glue to 1  cup water for 1 – 1 ½

            1 cup glue to 1  1/3  cup water for 1 – 2

To extend the open time (tack life) of the 1 – 1 mix, add ½  – 1 teaspoons of urea or salt.  Use a little less for the 1 – 1 ½ and 1 – 2 mixes.

To make liquid (room temperature) hide glue of the 1 – 1 mix, add 2 ½ tablespoons urea (or 1 ½ tablespoons salt) for each cup of dry glue.

Mixing procedures:

            add glue to cold water and stir.  Allow to soak for 30 minutes minimum.  Heat gently (double boiler or water jacket preferred) to 140o F, stirring occasionally.

For a basic unit, simply mix the glue in a glass pint jar and heat in a saucepan of hot water.

Lower gram strength glues generally are slightly denser and different production techniques will affect the density values so the above mixtures will vary slightly with the grade.  However, variables of temperature and water loss during use of the glue probably will have a more significant impact on concentration ratios than dry glue density.

Turned work

Turning is a process by which parts of furniture, such as legs and posts, are shaped while turning on a lathe. Turned work is found on Greco-Roman furniture. It is not certain whether the technique was actually employed in Egyptian furniture, though some members look as though they might have been turned. It was particularly in the shaping of wooden chair legs that Greek joiners used the lathe; the same sharp edges and deep moulding seem to be repeated in the legs of bronze furniture. It is possibly ancient turned work traditions upheld in Byzantium that are reflected in certain chairs of medieval form found, for example, in Norway; made of pinewood, the construction consists principally of turned staves (thin bars), some with appendant loose rings, some of them fluted (grooved). Similar turned chairs were made in Wales in the 16th century. In the 17th century, turned work was concentrated on pillars for cupboards and on ball feet but is also seen on chair and table legs, on which rich variations involving twisted and intertwining forms occur. Turned work in ivory also flourished in the 17th century. Except for the Windsor chair, or stick-back, however, the craft of the turner played no significant role in English high style furniture of the 18th century; it is similarly alien to French Rococo furniture.

Hide Glue – New Information Part VI

EXTENDING OPEN TIME, TACK LIFE

For those specific glue operations requiring an appreciable period of time for assembly before pressure can be applied, as in hand gluing of irregular pieces, the gluing of mortise and tenon joints, dowel work, and case goods assembly, the speed of set and period of tack of the adhesive may be varied at will through the incorporation of gel-depressant chemicals.  These chemicals, commercially available, are added direct to the warm hide glue in amounts sufficient to obtain the working characteristics desired – retarding the rate of jelling of the adhesive and prolonging the period of tack.  If sufficient gel-depressant is added, a cold liquid glue is produced which may be applied at room temperatures in the range of 70-85o F.  The preferred gel-depressant chemicals are those which only physically depress the rate of set, have no adverse chemical effect upon the structure of the glue, and produce a joint strength indistinguishable from that obtained in using a normal type warm hide glue.

Cold liquid hide glues are particularly well suited as the adhesive in assembly work employing the newer-type compression dowels and mortise and tenons.  In the use of these special assembly aids, the liquid glue furnishes sufficient moisture to expand the compressed wood to fill the joint rigidly and firmly, and the set of the glue is retarded to give a period of tackiness long enough to insure permanent adhesive anchorage at the joint.  The following cold liquid hide glue formula is suggested for this specialized application:

10 parts by weight 283-315 gram test hide glue

20 parts by weight water

  2 parts by weight gel-depressant (urea – a white granular   material, commercially available).

The dry glue is swollen in the cold water until soft (30-45 minutes); melted in a jacketed container at 145o F; the dry gel-depressant chemical added and dispersed in the warm glue solution; the adhesive cooled to room temperature is ready for use.  It is also possible to prepare liquid hide glue by simply adding the glue and gel depressant to cold – warm water, stir occasionally until a smooth liquid is obtained.

VENEERING WITH HIDE GLUE

Hide glues find wide acceptance in the production of high quality veneered panels both for core construction and laying of the highly prized veneer.  In this operation a thin layer or veneer of expensive wood is applied to a solid core assembly of lower priced wood.  This procedure permits wide utilization of our forest products and broadens the availability of attractive furniture of the office and home at reasonable cost.  Inlays of various designs, shapes, grain markings, and color are frequently used for decorative purposed on panels, table-tops, and the like, and are closely associated with veneers in their use and application.  All grades and types of hide glues may be used for adhesive purposes in this broad field.  Depending on the specific application and required length of tack, the warm hide glues, cold liquid hide glues, or modified warm hide glues partially treated with gel-depressants find use.  While extreme strength is not required in this field, the relatively non-bleeding qualities of properly prepared hide glue adhesives, their neutral color, permanence, and non-staining properties are qualities of interest and value to the user.

SIZING

The use of hide glue sizes in the finishing of quality furniture surfaces is not commonly known by the public at large.  In this process a dilute warm hide glue solution at approximately one pound of glue per gallon of water is applied to the wood surface and let dry.  The compression grain is raised and the glue fills the porous exposed wood structure.  On sanding, a glass-like surface is obtained, which is stable against moisture changes and which takes a lasting final stain or finish.

MOISTURE RESISTANT JOINTS

There are many instances in which, through trade demands, a moisture-resistant joint is desired.  Hide glue is readily made moisture-resistant through a simple, practical method which has been employed for many years.  The need for moisture-resistant joints, except for a few tropical and sub-tropical areas, has been greatly exaggerated. Furniture and musical instrument assemblies using unmodified hide glues have for many decades successfully withstood all usual climatic conditions the world over.

Where added moisture resistance is desired, the following procedure is recommended:

  1. Select the type and test grade of glue normally required.
  2. Prepare the warm glue solution following standard procedures.
  • To one face only of the wood joint to be assembled, apply with sponge or brush a solution prepared from one pint of commercial formalin and nine pints of water in which has been dissolved ½ pound of borax.  Allow the excess moisture to be absorbed from the surface of the wood.
  • The glue solution is applied to the matching face of the assembly.
  • The formalin-treated and glue-treated members of the assembly are then brought together and placed under pressure.
  • The glued assembly, after removal from the clamps, is allowed to season for from five to seven days, to permit a gradual even development of moisture-resistant properties.

This simple procedure effects a controlled tannage of the glued bond, providing moisture-resistance while still maintaining the strength and shock-resistant properties so characteristic of hide glue joints.  Note this tannage of the glue film is not reversible.  So the hide glue characteristic of being reactivated with moisture and heat is completely eliminated.

GLUE BOND FAILURES

In all adhesive work there are occasional joint failures.  With hide glue and its inherent margin of safety factor and a tensile strength far in excess of wood, such joint failures as may occasionally be experienced are more properly defined as gluing failures.  Among the more common causes of gluing failure are:

  1. Improperly seasoned wood.  A kiln-dried wood is desirable wherein the excess moisture has been properly reduced to the moisture content equilibrium under which it will be used (8 to 12% moisture), with freedom from case hardening and internal stresses.
  2. Poorly dressed or machined wood.  Glue is not a filler – the joints should be true.
  3. Insufficient clamp pressure.  Sufficient pressure should be applied to bring the individual members into alignment, squeeze out air and excess glue, and hold the members in rigid position during development of adhesive strength.  Pressure of 100 to 200 pounds per square inch are recommended.
  4. Excessive clamp pressure.  Pressures over 150 to 200 pounds per square inch are generally unnecessary, and are apt to squeeze out glue essential to formation of a sound joint.
  5. Removal of assembly from clamps before sufficient development of joint strength.
  6. Machining or surfacing of joint before full development of joint strength and equilibrium moisture content of joint have been attained.
  7. Improper glue solution for specific assembly.

If the above listed variables are properly under control, the glue solution at 140o F in case of warm hide glue solutions, and the room and wood temperatures at 72-80o F, the proper glue concentration will provide:

  1. Adequate wetting-out of the wood surface.
  2. Proper transfer of glue applied to the one side of the joint to the adjacent face after pressure is applied.
  3. A tacky, slightly stringy glue film at the joint just as pressure is to be applied.
  4. Extrusion of a small amount of tacky, fairly heavy-bodied excess glue from the joint as pressure is applied.

QUALITY CONTROL

Careful examination of a few test joints, as being processed, and with the above conditions in mind will enable the operator to evaluate the conditions present and modify the basic glue concentration as required.  If the glue concentration is too heavy, imperfect results under a) and b) will be found.  If excessive glue is extruded under d), excess glue was applied to the joint, or the glue solution was too thin, or pressure was being applied too soon.  If relatively no glue is extruded under d), insufficient glue was applied, or the glue was chilled or dried before application of pressure.  “Starved”, “chilled” and “dried” joints may be eliminated through proper variation in glue concentration and gluing technique to insure the condition under c).

All hide glue suppliers are in a position to offer more detailed information and technical service concerning the use of hide glue as an adhesive, and with particular reference to its use in woodworking, to those who are interested.

Hide Glue _ New Information Part V

GLUE GRADE SELECTION

The proper choice and selection of the hide glue adhesive for the specific application greatly simplifies all gluing and provides fast, efficient operation at maximum economy with consistently strong joints.  For most adhesive applications, it is desirable to use grades #135 through #379.  For general repair work, grades #135 through #251 are commonly used as the lower ratio of water to glue (versus higher gel strength grades) permits depositing more glue (higher solids) with adequate open time.  Glue makes the bond, not water.

For assembly and edge-gluing there are three major groups of hide glue, all providing a wide margin of safety factor and a tensile strength far greater than that of wood itself, and differing principally only in inherent strength, elasticity, and shock-resistant properties.

  1. For maximum strength and shock resistance

Jelly strength grades testing 315-379 grams

  • For average strength and shock resistance

Jelly strength grades testing 192-315 grams

  • For non-critical strength and shock resistance

Jelly strength grades testing 135-192 grams

For soft porous woods, principally the conifers, a fairly heavy-bodied adhesive is employed; for dense, non-porous woods, such as maple, birch, and some of the oaks, a moderately thin-bodied adhesive is desirable.  This variation in the glue concentration of a given test grade of glue directly leads to consistent gluing results through

  1. control of the thickness of spread of the adhesive,
  2. degree of penetration into the wood and proper anchorage of the adhesive,
  3. holding of the adhesive film at the joint,
  4. desired speed of set and length of tack of the adhesive at the joint face. 

The following table gives average formulations for the various test grades of glue for assembly gluing where wood and room temperatures are in the range of 74-80o F.

Typical Water to Glue Ratios

Glue Grade (Test in Grams)Porous Woods (Weight, Water to Glue)Non-Porous Woods (Weight, Water to Glue)
3793 – 13 ¼ – 1
3472 ¾ – 13 – 1
3152 ½ – 12 ¾ – 1
2832 ¼ – 12 ½ – 1
2512 ¼ – 12 ½ – 1
2222 – 12 ¼ – 1
1921 ¾ – 12 – 1
1641 ½ – 11 ¾ – 1
1351 ¼ – 11 ½ – 1

The preparation of the warm hide glue adhesive solution follows the standard procedures previously described.  The glue is maintained at 135o to 145o F and applied at this temperature for best results.

The following table gives typical viscosity values for solutions based on the percentage of glue content.

Approximate Viscosity in Centipoises at 140o F for

Dry Glues of Given Grade Test and Millipoise Value

  % Glue ContentHigh Gel 379 Gram 131 mpsMedium Gel 251 gram 92 mpsLow Gel 135 gram 58 mps
12.513.19.25.8
1524156.2
20664017
25162 }9734
30420 }225 }69
351060}490 }160  }
4024601030}265  }
501269057201190 }

Depending on the tack and set desired, the typical viscosity during use will be 150-500 cps.  Rarely would it be over 1000 cps.   The three } values are the typical ranges that would be employed for each grade 135, 251, 379. For production-line edge-gluing, where speed of operation is an economic factor, the fast setting properties of a warm hide glue adhesive film with resultant immediate tackiness, holding of the adhesive at the joint face, control of bleeding-in of the adhesive, and fast development of initial joint strength are factors of great value that are unique with hide glue.  Considerable latitude in the speed of set and corresponding length of tack is possible with hide glues.  For slower speeds of set the lower-testing grades may be employed, or the ratio of water to glue may be increased for the specific glue.

Decorative processes and techniques

Whether constructional principles are exploited as a motif or elegance of overall shape is stressed through stylization, every piece of furniture can be embellished in one way or another. A piece of furniture may be embellished by effects produced in the structural wood itself or in another kind of wood added to the first; that is, by carving and turning or by inlay work. Alternatively, the piece can be decorated by the addition of materials other than wood, such as bronze, ivory, or marble. Finally, in the case of furniture meant for sitting or lying on, there is the possibility of textile enrichment in such forms as upholstery, loose covers, and cushions.

Carving

There are examples of furniture carving in Egypt at the time of the pyramids: animal legs of cedarwood on biers, beds, and chairs; and ducks’ heads terminating the legs of folding stools. Elegant carved headrests took the place of pillows in this hot climate.

Whereas carving does not appear to have played a significant part in Greek and Roman furniture, it was a dominant feature of European furniture of the Middle Ages. The fronts of chests bear Gothic perpendicular tracery (decorative interlacing of lines) in imitation of the decorative stonework found in ecclesiastical architecture.

Another source of inspiration for carved ornaments in bourgeois furniture was the ecclesiastical wood carving found in choir stalls and altarpieces. The art of the wood-carver also flourished in Islam during the Middle Ages, especially in kiosks (open pavilions), oriel (large bay windows projecting from the wall and supported by brackets) windows, and Quran lecterns. The most original and remarkable form of medieval carved ornamentation was the linenfold, which resembled folded sheets of linen laid on the surface of the wood. Although the motif was widely known, its origins are obscure.

During the Renaissance, wood-carvers changed motifs: new ornamental riches, partly inspired by the forms of Classical antiquity, began to adorn cupboards and chests. Acanthus leaf designs, strapwork (narrow bands folded, crossed, and sometimes interlaced), Moresque designs, the auricular (resembling a flowered Alpine primrose) style, bunches of fruit, and scrollwork for over a hundred years dominated the figure-carving repertoires of European cabinetmakers.

During the 17th century the fashion for carved work at first receded but came to the fore again in the console tables (tables designed to fit against the wall), mirror frames, and high-backed chairs of Court Baroque. In striking contrast to lacquer cabinets of Japan, sumptuous, gilded carved work became popular on the stands invariably made for them when they were imported to Europe.

In the 18th century, wood-carvers enjoyed a final splendid period of prosperity when the Rococo style of ornamentation called for the plastic effects obtainable through carving. Whole panels of woodwork, doors, mirror frames, chairs, and settees were adorned with the finest wood carving, featuring combinations of mussel-shell patterns and naturalistic vines and plant tendrils. Even in English furniture of more sober design there were ample opportunities for carved work; for example, in the many chairback variations in the Chippendale manner.

American cabinetmakers were particularly skilful at carving block fronts (the sides curving forward and the middle receding) on the drawers of chests of drawers, and the English at making tea tables with piecrust (scalloped) tops.