Too thick solution, sometimes the ready to use shellac are a bit on the thick side to get the layers even and nice. Poor in a bit of denaturated alcohol if it turns out to be on the thick side.
Going over the surface twice when applying shellac can cause hickups, wait a minute or two until it has dried, then a new layer. Even motions in one direction. In the worst of case the alcohol can end up dissolving and removing the newly applied shellac.
I guess a lot of things can go wrong in theory, but it usually doesn't. Start with a clean surface and the new shellac will bond well, I think some slightly buff down the sheen on older furniture when redoing the top layers, but of course you can't do that too much over decals. I have seen lacquers flake for some reason, including shellac, but I can't say I know what caused it, and it has been older machines. I have seen people apply shellac with a brush and get a good result, I think the reason for the cloth ball is it's easy to get a nice result, and buffing out the day after. (The use of pumice powder too, but that's for wood).
Last edited by Mickey2; 08-29-2019 at 09:22 AM.