For the woodworker, quite often the hardest part of any job is the finish. Not only do you have to choose a finish that suits the job that you’re doing, because it’s not a task you do every day (unlike a professional paint sprayer), it takes longer to set up and finish the job, and much longer to acquire the skills and experience to know that it will go right every time.
As a luthier, it’s even harder. So I’m writing this not for luthiers per se, but for the hobbyist builder who may run into the same problem I have just hit, and solved!
Many of us like our natural woods, but like a thin finish and a deep shine, like looking onto still water on a clear day. That’s tough to get. So the combination we use is a wood stain and Nitrocellulose Lacquer. Looks fantastic when it works, but certainly in the UK there isn’t always a huge range of choice in Water based dyes, especially ones that don’t raise the grain. You won’t find them in your local hardware store, you’ll need a specialised vintage finishes retailer like Classic Finishes in Norwich (who BTW are very good and really know their stuff) . And we all know that oil or spirit based dyes and Nitro is a bad mix. And here’s the problem:
Fisheye is a condition where lacquer refuses to adhere or sit on small areas of the object, creating voids in the finish which look as the name suggests, like fish eyes.
Quite often, if it’s a dye reaction then the problem will exist all over the piece. You can rub it back and spray again, but the problem still exists. Layer after layer of spraying and flatting, and the problem returns.
This is because the contaminant that is causing the problem simply gets ‘lifted’ to the new surface by the solvents every time you spray, so you can never rid yourself of it.
One solution is this stuff (or something like it):
This is Starchem’s PA-1 paint additive. One or two drops into your mixed lacquer before loading to your spray gun and the problem tends to go away. Rub back a bit before you spray to get as flat as possible before you start.
It works by breaking the surface tension of the lacquer and forcing it to flow level. Once you have used it on a piece, you must use it in every layer. You must also use it for spot repairs even years later because it is in itself a contaminant. (Stick a note inside the control cavity!)
But you say, how do I do that? I’m using rattle cans and don’t have a compressor or spray rig! Fear not – help is at hand!!!!
Unfortunately, unless you know a paint supplier that still does Nitro from stock (i.e. makes up its own colours and puts them in rattle cans for vintage car restorers), then your rattle cans cannot be doctored. A good supplier will drop a couple of drops of additive in a rattle can if you ask. But we don’t have that today, so how to solve the problem?
I had this with this particular headstock, which I had to uncover and re-dye with spirit stain due to the lightweight tuners I ordered not being deep enough! (My mistake, forgot to take the washers into account from the spec sheet!)
So I had already used PA-1 to spray the whole instrument, because I had some fisheye, but this is not the best way of dealing with the problem ‘before’ it occurs, it’s a get out of jail solution once you’re already in trouble.
And this is where another ‘wonder product’ comes in:
I used this as a barrier between the spirit stain and the nitro. I still used a drop of PA-1 because I was blowing in over the edges of the previous finish, but the Tru Oil creates a barrier which isn’t rejected by either the Stain or the Nitro.
I always leave it a day to dry before I spray, but it’s so simple and easy to use, and pretty cheap too, that it’s just the easiest answer to spray paint compatibility issues that I have yet found. You can use it as a sanding sealant, and enough layers will practically grain fill (if you apply it using sandpaper to create a mulch with the dust as you rub). So you can use it under a cellulose spray sealant, primer, base colour or just Lacquer. Rub it in, flat it and away you go!
So there you have it – another problem solved!