Most people simply use commercially available “denatured” alcohol. Denatured alcohol is a general alcohol-based solvent used for a variety of applications across many industries.
Denatured alcohol at 95% is the solvent for all shellac flakes.
Isopropyl rubbing alcohol is no good for thinning shellac because it contains about 30% water. The water will cause the shellac to turn white, or “blush.” If you have access to 95-to-100 percent pure propanol or isopropyl alcohol, you could use it for thinning without a problem.
Shellac can be redissolved in alcohol, so it's easy to just soak the brush in some alcohol to soften the bristles the next time that I need to use the brush.
To make a general clear shellac varnish, in a clean glass jar, add 1 part (by weight) dewaxed shellac to 3 parts Methylated Spirits. Stir or agitate till dissolved (approx. 30 minutes) and then thin with extra Methylated Spirits to suit.
Denatured Alcohols (methylated spirits) for Shellac.
Mineral spirits won't dissolve cured finishes such as polyurethane, lacquer, varnish, and shellac, so it can be used to clean wooden surfaces like furniture and floors.
Brushes affected by dried-on shellac may benefit from an extra wash in mineral spirits and then a soapy water wash once all product has been removed.
Mineral spirits is similar to naptha in that it won't harm the shellac, but could leave a slight bit more residue. DNA runs the considerable risk of damaging the surface since it is a primary solvent for shellac. Lacquer thinner also runs a risk, since some lacquer thinners contain alcohols that could dissolve shellac.
Turpentine cannot be considered a solvent in the same way that alcohol dissolves shellac or water dissolves salt.
Removing shellac. Paint your surface with Methylated Spirits (denatured alcohol). Leave it to soften slightly and then moving in the direction of the wood grain, rub back the old shellac finish with 0000 steel wool.
Isopropyl alcohol is fine for mixing shellac. I believe that your mistake was not shaking/stirring from the beginning.
I came across an interesting article in FWW#151 (Oct 2001) that explains the various thinners commonly used to dissolve shellac, and also recommends adding a very small amount of Pure Gum Spirit Turpentine to already-liquid shellac to slow the drying time of the shellac (acts as a retarder), allowing you to keep a wet ...
Shellac is soluble in alkaline solutions of ammonia, sodium borate, sodium carbonate, and sodium hydroxide, and also in various organic solvents. When dissolved in alcohol (typically denatured ethanol) for application, shellac yields a coating of good durability and hardness.
Dissolving & Mixing Flake Shellac
Soak the flake shellac in about 1/2 of the total alcohol to be used for 24 hours or longer (cool room temperatures will slow the process; pulverize the button shellac to speed dissolving) stir occasionally and when dissolved add the balance of the alcohol.
Acetone and mineral spirits are not the same, and should not be treated as if they are. Part of the confusion comes from the fact that both are used as thinners . Painters commonly use mineral spirits, for example, to thin the paint that they put into paint sprayers. Acetone, on the other hand, is used to thin lacquer.
"…the objective is to remove the shellac from the brush, roller, etc, not to thin the shellac that is still in the brush. Now, the explanation; just as mineral spirits/paint thinner won't completely remove varnish from a brush, neither will alcohol alone completely remove shellac from a brush.
Denatured alcohol works best as a solvent for cleaning. But, you cannot use it to thin paints. Turpentine – Like mineral spirits, you can use it to clean brushes or thin paints. Charcoal Lighter Fluid – You can use it the same way since it is made of mineral spirits.
“Paint Thinner” is mineral spirits, but in a less refined form. It contains other types of solvents, which makes it a lot smellier and more volatile.
Repairing a Shellac Finish
Shellac is not alcohol- or water stain-resistant, but damage caused by either one can be easily repaired. You can buff out a white water stain on a horizontal surface (such as a tabletop) with a small amount of lemon oil and #0000 steel wool.
Physical and Chemical Properties
Fresh shellac is soluble in ethanol, acetone. Shellac becomes insoluble with age. Insoluble in water, turpentine or mineral spirit.
MIX RATIO. Dissolve Shellac in methylated spirits at the rate of 250g of Shellac to 1L of Methylated Spirits.