De-Waxing Shellac Under Difficult Circumstances

Removing impurities from shop-mixed shellac in a world where impurities come with the territory. April 29, 2012

I am in Nepal and I can't find much of anything that's not adulterated with something else. For instance, the turpentine that I have found lately is adulterated with kerosene and the thinner is who knows what. It could be mineral spirits - I don't know, but would venture that it's the cheapest thing that will thin paint and is probably not refined well.

I bought 1 kg of shellac buttons yesterday and dissolved them in alcohol to prime my newly made air-dried/knotty-pine window frames. I made a 3lb cut and set the bottle out in the cold overnight. This morning there was no apparent movement of wax to the bottom. It was all very much suspended in the solution. Unfortunately, I can't wait a few weeks for this to happen, schedules and all.

I have read that adding mineral spirits or even turpentine will cause the wax in the shellac to coagulate and thus speed its removal. The problem is, as I mentioned above, I have no idea what effects kerosene or the other possible adulterants might have on the shellac.

Forum Responses
(Finishing Forum)
From contributor B:
I'm not an expert, much the opposite, but I have been dewaxing orange colored shellac following shellac shack. I find the decanting method to waste too much material, but I've been told by a chemist that none of these methods remove 100% of the wax.

From contributor Y:
Using a Buckner funnel along with a 500 ml vacuum flask and 1 micron filter paper will eliminate 98% of the natural wax, the same amount you would find in the best thin flake German imported Lac flakes. Personally I run the shellac through more than once with new filter paper.

Your reading of using mineral spirits or turpentine is merely a way to knock the resin out of solution, thus separating the resin portion from the wax, much as it will do the same with other evaporative finishes such as nitro lacquer or solvent acrylics. With this you will still have a time separating the lac from the wax as they don't form a complete separate layer or mass that can just be pulled apart or separated much as the nitro lacquer will do, allowing you to simply remove the glob of CN from the remaining solvent mix for further drying out of the solvents.

It is well documented by the Shellac institute in India since the 70's that oxalic acid has a detrimental effect on the lacs in the processing stages of development. It is always best not to add anything to shellac but anhydrous ethyl alcohol or anhydrous isopropyl alcohol. But since it is extremely difficult to obtain such as the first, you can purchase the most widely used SDA formula #1 Den. Alcohol. Be cautious though, the denaturent is Methanol (5 gallons to 100 gallons) and its molecule is small enough to permeate and pass through skin tissue and enter the blood stream which the body then turns it to poisonous material. If none are available to you, then at least try to find a better one than you have now.

Oxalic increases moisture absorption of the lac and shellac end products. It reduces shelf/storage life, and imparts other bad qualities such as rapid polymerization, not a good thing at today's lac prices which continue to rise. Itís best to stay with vacuum pumping.

Three things may be the culprit for why your lac did not settle out. One, your alcohol is not pure enough and has too much hydrogen oxide (water) content, two, as you already are aware of, your thinner may be too weak also or not even what is marked as what it is, and three the shellac should be thoroughly dissolved and thoroughly mixed before trying to add aliphatic hydrocarbons to achieve the shocking of the resin/solvent separation. Try to set yourself up with the vacuum system and stick with that. It has served me well since the 70's.