I thought I had the surface of my bass's body completely flat after pore filling, so I went ahead and started spraying lacquer coats. After letting all the coats of lacquer cure on the body for 72 hours, the pore started to become visible again. Is there any way that I can fix this without stripping the lacquer off?
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No need to strip the lacquer off. Now, use the lacquer to fill any remaining pores or roughness. Lightly block sand with 600 grit paper, trying not to go through the lacquer. Clean off the dust and spray more coats of lacquer. Repeat, repeat, until it's all glass smooth. Then spray your last coats of lacquer, let it fully cure, do a final level sanding with 1500, then buff it out to a gloss.
The pore filler is a first step, to fill most of the pores and dimples, and save some of the coats of lacquer. You can do the whole process with lacquer, but it takes a long time and a lot of coats. And a lot of sanding.
To add to what Bruce said, if you have a particularly stubborn area you can spot fill the individual pores. Just dip a tooth pick into a small cup of laquer and place a tiny drop into each of the pores. After they are well dried you sand them flat and spray another coat over the top.
It can be hard to tell the difference between stubborn pores and orange peel on the surface of the finish itself. If your spray setup isn't setup just right you may get some slight roughness that's somewhat similar to an orange. You can usually sand that away without burning through the finish.
Fortunately laquer is a very forgiving finish. It melts back into itself so small repairs can be blended in more easily and you can almost always sand it back and apply more coats. Unless I missed it you didn't specify how many coats you applied. I generally spray 3-4 coats a day apart until I've built up at least 12 coats before I start thinking about polishing it. Most laquers have a lower solids content that a lot of more modern finishes which means that more of the can is solvents that dry and evaporate away as the finish dries and less solid material remains. It helps to build the finish a bit more than some other finishes before you start blocksanding it back flat.
It can be hard to tell the difference between stubborn pores and orange peel on the surface of the finish itself. If your spray setup isn't setup just right you may get some slight roughness that's somewhat similar to an orange. You can usually sand that away without burning through the finish.
Fortunately laquer is a very forgiving finish. It melts back into itself so small repairs can be blended in more easily and you can almost always sand it back and apply more coats. Unless I missed it you didn't specify how many coats you applied. I generally spray 3-4 coats a day apart until I've built up at least 12 coats before I start thinking about polishing it. Most laquers have a lower solids content that a lot of more modern finishes which means that more of the can is solvents that dry and evaporate away as the finish dries and less solid material remains. It helps to build the finish a bit more than some other finishes before you start blocksanding it back flat.
^^Yep, all of this.
Additionally, you can also use CA glue to fill stubborn pores... even in the middle of lacquer top coats as shown here on this Strat with a ziricote top. Those are drops of CA, not nitro. They got sanded flat, then more nitro on top. You cannot see them in the subsequent coats.
Also, if you're using rattle can nitro... keep in mind, that stuff is much thinner than shooting it full strength with an air spray rig, etc.
I shoot nitro a lot, and using nearly straight, unthinned product, I usually put 7-10 top coats on. With spray bombs, you may need to double that.
That stuff is purposely thinned so that it sprays well out of a can. That is not a criticism, it's just a fact and a quirk of the product... and it makes it far more expensive to use that using an air rig and straight product.
Another technique that I use is to roughly level sand every 3-4 coats (double that for rattle cans). I generally use 800-1000 grit for this. It keeps the overall finish thickness down, while filling and leveling those pores. It doesn't need to be perfect, but it yields great results at the end with much less orange peel and less work to level sand after the fact.
The bottom line is this: Pore filler and nitro both shrink back... sometimes quite a lot, especially within the first few days. Plan for it and allow for it. Sand back periodically and shoot more coats than you think you need. That isn't a goof-up or a mistake, that's how it is done, there really are no shortcuts. Be patient and do the work; all of it.
This carries through into the curing process. Let that nitro cure for a while (3 weeks minimum) before you level sand and polish. The longer you wait to level sand, the fewer imperfections will telegraph through to the surface.
Good luck and let us know how it goes!
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