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Still not sure how a harder foundation would prevent scratches? Vinyl sealer by design is softer and more flexible than top coat chemicals, kind of the opposite rational? But admittedly I don't know jack.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Roughly what ratio of retarder to lacquer do you use? Are you also using thinner? It's also been suggested in this thread to thin the satin lacquer with a combo or lacquer thinner and acetone for better flow and leveling.

Sorry, you are of course correct.
Sheen, as in the light's reflection off the surface, will not differ between one coat on top and all coats being flattened.
The effect I was describing was the scattering/diffusion? of light by the flattening agent contained in the base layers.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I was taught years ago that proper layering of finishes had the rule of: you can apply a softer finish over a harder finish but not the opposite.

The logic behind this was that with a softer base finish cracks would possibly show up in the top layer because of movement differential. After years of reflection (and admitted confusion concerning this rule) I currently hold it as a rule to be applied for refinishing, e.g. there is already a substantial build on the product and one is adding more.

In the case of a vinyl sealer, we are talking about a, when correctly applied, thin base coat that acts as a separation of the wood from the real finish. Because of whatever chemistry is involved (as a note I've always used a compatible vinyl sealer, again because I was taught to do so, and had no issues on that level..other issues, well sure) the vinyl coat is purported to bond better to the wood and allows the compatible finish coats to bond well to it.

other issues? Lesson learned: did a massively difficult project of taking a 21' bar and converting it to 30' long...the finisher couldn't get the stain dark enough and ended brushing the last coat on and leaving it to dry for a week...this was MinWax stuff that has a sealer built in (e.g. additional coats really don't do much as the wood is already sealed and won't absorb more stain)...in the long run the finish failed as for all intensive purposes said last layer of stain he applied was just a layer of dark colored dust...the finish bonded to that, problem was the layer of 'dust' wasn't bonded to the wood work. On a personal level I pushed the envelope one and darkened the final product by using gel stain between coats (in an 'approved methodology used by painters) and ended up with a 'stable' product, one that passed the hit the test panel with a hammer to see what happens, yet I could take a thumbnail and scratch it right off...bleh...luckily I've never heard anything negative back about that.

Anyway, there indeed does seem to be confusion about the 'rules' of how to layer different products...logically the concept of a hard base and softer top makes sense...but most likely there is some middle ground where a harder top coat would work over a slightly softer base. Don't know, and since I changed my path early in college away from chemistry I'll probably never know on a true level, and the fact that since I see no great reason to do massive experiments, which require time and $, to prove/disprove any points just hammers that point home. There is a wisdom in following the teachings of others, and that is what the build up of knowledge is all about.

Just a bit, 5% or so. just want to increase flow a little bit.

I don't like acetone for a few reasons. One it is very aggressive and can re-wet and re-flow the coatings I have already put down and spent my time level sanding....I hate things that mess with work I have already done. Also the reason most people add acetone is another reason I dislike it as an additive.It reduces surface tension drastically, making the coating flow out really smooth ....why they use it.....but in addition it is making your final coat more prone to runs and sags and it also makes the film build much thinner. Like cuts the film thickness in half or better. so now your top coat of satin is so thin it wears away to a shine in a few months. Unless you spray more coats....which leads to surface texture (orange peel).....

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

What grit is most appropriate to level the finish with before the final satin coat? Do you think 220 is sufficient? Or will the 220 grit sanding scratches be noticeable in the texture of the final satin coat? Maybe it should be leveled with 320 grit or higher?

I have always used 800 grit with good results.

800 grit wet/dry paper with soap and water or 800 grit dry stearated?

I use the 3m gold fre-cut paper that I get from stew mac and use it dry. My finish is nitro.

So I'm having decent results now that I've taken everyone's advice and have sprayed a number of guitars. However, I'm still getting tiny imperfections in the finish. It's not quite perfectly flat and there will be tiny little bumps and pimples in the finish. I'm spraying in a semi professional spray booth with furnace filters filtering the air as it enters the booth. Maybe I'm just being too much of a perfectionist? I was trying to take a photo of the imperfections I'm talking about but had a hard time capturing it in a photo. For the final satin coat I am using equal parts precat satin lacquer, acetone, thinner and roughly 5% to 10% retarder. I keep level sanding the surface with 800 grit and 0000 steel wool and trying again and again for a final perfect coat.

Have you overlooked the most common source of contamination in the spray booth aka the operator?