Hand made guitar amplifiers, Modification and upgrades, Guitar Amplifier Repair
My experience with shellacking a tweed cabinet
This is my experience and opinion. Yours may differ. Some advice on shellacking a tweed cabinet.
1- Just about everybody tells you to thin out shellac with denatured alcohol. DO NOT. The first thing you will notice about painting with shellac is that it is the consistency of water. The more you thin it the more coats you will have to apply, and it is just not necessary.
It doesn't hurt to have a can of denatured alcohol on hand for brush and or spot cleanup.
2- If doing it indoors, open a window a bit, shut off your phone and put it in your pocket. You will thank me for that. If you wear glasses to see close, then put on goggles over your glasses. If you wear glasses to see far, take them off and put on goggles. Do not wear clothing that you care about. Clear everything and anything in a 3'-4' radius on your work table/bench whatever, that you want to keep clean. Put down a clean flat drop cloth with no ripples in it. If you use a brush, shellac spits and sprays with every brush stroke. It will get in your eyes, on your glasses, on your phone, on your clothes. You have been warned. Vinyl or latex gloves wouldn't hurt either especially with tinted shellac.
3- Remove all hardware from the cabinet and remove speaker baffle if it is not too difficult. Otherwise you need to mask it off. The baffles on my amps come right out with the release of four screws.
4- If your amp has feet, remove the feet and use the screws if they are long enough by screwing them partially back in and allowing the amp to stand on the screws. If they are not long enough then get yourself some longer ones.
5-Make sure you have good lighting.
6- Make sure you have a chopstick or something similar to mix the shellac thoroughly. It should be mixed a few times while you are working.
7- Vacuum out the cabinet thoroughly. Vacuum the exterior as well to get rid of dust.
8-Don't dip the whole brush in the can. A 1/4" or so will do. Start spreading the shellac and keep moving but make sure you spread it evenly. Watch it closely angling your head to catch the light just right. Watch for stray brush hairs or anything that might come in contact with the surface that you would not want to see. DO NOT TAKE YOUR TIME. This stuff dries fast and you will mess up your cabinet if not ruin it if you stop to take a call, text or email. You must keep moving.
9- If you see a stray brush hair, take note of it and come back to it after you have finished the coat.
10- Let it dry for about an hour or so.
11- DO NOT SAND in between coats. That is the dumbest advice I have heard in a long time.
Tweed covering is NOT wood. It is a completely irregular surface with ripples, highs, lows and everything in between. Sanding will only affect the highest points of the material and if you sand to hard you will cut right through the coat of shellac and start sanding away the tweed itself. Don’t do it.
12- Before applying a second coat look the box over carefully for any stray brush hairs and carefully pull them out with the help of something sharp. I use dental tools with sharp points.
13- If your first coat was amber shellac or tinted, you need to decide whether you want it to be darker or not before applying the second coat. Same holds true for the third coat as well. The photos in this article are 3 coats of amber shellac.
14- Three coats are a minimum in my opinion. It can be 3 coats of clear, or 1 coat of amber/tinted and 2 coats of clear, or 2 coats of amber/tinted and 1 coat of clear or 3 coats of amber/tinted. You can always add more coats of clear shellac to build up the finish without the risk of it darkening much.
Click on a photo below to see enlarged picture.