French polishing is an artistic medium. When utilising shellac, mistakes are common and nothing is more stressful than having to redo hours of effort to remedy issues that you once believed were beyond your control. However, most of the time, these issues were entirely preventable. Beginners frequently get into issues with cracking, slow drying times, blooming and many other issues. The simple answer to resolving these issue is to stop using methylated spirits. Methylated spirits means differently to those in other countries, but those in Australia I’m referring to the “Diggers” brand you will find on the shelves in Bunnings stores in fact in all hardware stores.
Up to 30% of water can still be present in methylated spirits while maintaining their “methylated spirits” name. The core of many issues with French polishing and effectively applying shellac is this high water content. Dissolving the raw shellac flakes can be the very first issue you run into when employing methylated spirits. Whilst methylated spirits may be a great cleaning agent, it is definitely not for dissolving shellac nor even using it once dissolved due to the high water content.
Now I’ve met many old timers who have used methylated spirits and swears by it. That being the said I have not ever seen their work to verify their oaths.
DAA which is Denatured Absolute Alcohol is 100% pure Alcohol. Alcohol dissolves raw flakes more quickly and has a shorter drying period than methylated spirits, which contain just 70% alcohol and 30% water, which can easily produce blooming and other potential issues. Blooming are white blotches that appear on the surface and is very difficult to fix. Blooming is caused by the water content in the Methylated spirits and the moisture in the air. Even though blooming can occur even with 100% alcohol it is some what minimised.
DAA in Australia is not sold in hardware stores like Bunnings or Mitre10. Only specialty stores that sells shellac and other woodworking stores sells them. Yes, even Diggers sell them. However, please be aware that there are many grubs, sods, skuz buckets out there that will over charge and ask as much as $200 for 20litre drums. The price is $90 for 20L and as little as $10-$12 for a 1L.