Hello all again, this forum really proves to be helpful.
I want you to shed me some light on this one. I hope it's okay for you to talk solid body guitars, mainly electrics. However I was asked by a customer which is in fact a good friend of mine to do a whole repaint on a vintage bass guitar. It will be solid white, no fuss with transparency.
I know guitars mainly come with nitrocellulose and polyurethane finish. But what does that mean? I know the chemistry of paints and I clearly know what different bases are, but I was wondering does this mean that only the clearcoat is poly or nitro or the whole paintjob including the lacquer itself?
I'll be using pro lacquers for car repair and I know a source that can get me anything, I just have to decide what to use.
Another question would be what to use as a primer? Car bodies mainly consist of zinc-coated tin so etching primers are used to ensure they bond well to the bare metal because zinc makes it slippery. Should I avoid etching primers on wood? What about the base, can I go with regular polyester? I can also get nitro, poly and even epoxy primers.
I know it's generally best to use all of the same base, they will be however from the same manufacturer (Sikkens), but then again that's how you paint a car, not guitars. I worked often in friends car body shop so I know the job in details, but I never fooled around with hard lacquers on wood.
Nitro, poly, and acrylic. They are being used stand alone or some combo, in layers.
It sounds like your going to use acrylics. I know nothing of them... other than Fender did use them in their metallic finishes.
For Nitro, some use 50/50 (nitro to thinner) mix, or vinyl sealer, or shellac as a base coat. Their may be others but these are the ones I know of and have worked with.
For Poly, most of what I know is that you will need something called isolator for a base coat.
It is safe to assume that you would want to use the same manufacturer from beginning to end and the manufacturer can help you trouble shoot an issue with the reactions of THEIR products to products/products to different woods. There could be issues with using different brands threw out the process or none at all.
This is really just shavings off an iceberg..... Hopefully someone else will bring some light to your question(s).
If I were doing one like that I would put a clear coat of Nitro on then white latex then clear coat with Nitro. Maybe someone like Rusty will jump in here and give you some addvice. Bill...........
I've got to be brief as I'm on the fly today - Ideally, a full nitro schedule is my choice for electrics but, a lot of modern finishes are polys or combinations of Poly and nitro finish coats etc - lots of combinations out there.
If you are going to use an auto finish just use a standard gray body primer (that what it is called as a generic) - A lot of body primers are two pack epoxy and I've used them with success for one-off special jobs - but, you need to make sure you can get them on in quick time if you need to use multi coats on grainy wood, as they need to bond to themselves. Use an Auto "bog" filler coat (sqeegy and sand) if the grain needs to be filled before applying a primer coat. Poly finish coats or acrylics are then applied to the sanded down primer. Be careful to not sand through the primer coat as the finish coats show this very well if the substrate/base coat is breached exposing bare wood.
There is no need to use an etching primer but I recall a lot of them are etching anyway - it probably won't hurt anything, but I've never really given it any thought - if you can get non etching primer (ie: a filler type primer) then it's an obvious choice to use it.
WARNING: some auto two pack finishes are dangerous to breath in or get on the skin and eyes - pay attention to this and don't think its not important.
The auto acrylics are a pain in the butt, especially if you don't have a curing oven - I've sprayed the Fender Acrylic schedules and will probably not do it again willingly.
If you are going to muck around with hybrid finishes - the poly/epoxy goes on first and the nitro goes on last (unless you wish to ask yourself......."am I feeling lucky"...and, the info I have given you will keep you out of trouble - it's not comprehensive and there are exceptions but it works generally. If you have specific questions please ask and I will get to them in a couple of days if that is OK.
Thanks for your time and information Rusty. I hope Tadej was abale to use the info you have given him. Bill.............
Back before the internet existed Luthiery was like some kind of black art and was usually practiced behind closed doors with secret handshakes and variable measures of success - I suspect a lot of my colleagues have similar stories to me about some of the epic failures that we have been a part of ! A lot of work was done by trial and error and a lot of good intentions and good ideas were quickly found to have shortcomings.
Anyway bloke, yr not alone and yr in good hands with the gentlemen on this forum - it only took me 10 years of full time work to finally accept that I could actually call myself an instrument maker without fear of lightning striking me down. Good luck, Rusty.
Hello again, guys.
Thank you again for putting in your best effort, I love it when people are willing to share knowledge with those that are eager to learn. I'm replying late, we had a hell of a weather here, maxing at 36 degs celsius all the time and humidity was through the roof. I had one randy rhoads waiting for a fret leveling and it was my main obligation this week. What I could finish in a day or two took me whole week because of the unbearable heat.
I still haven't got a chance to meet up with a buddy of mine that owns a body shop to go through his extensive palette of coatings... but I have concluded I will avoid nitro clear coats if it is up to me to decide what to use. Been having a poly finished strat for ten years now and I love it how tear-resistant it is. And I especially don't like the nitro patina that develops over the years
I suppose I won't go wrong if I do a normal priming, then nitro or acrylic lacquer and finally a poly finish. Russell, what's a good amount of coats? I'd prime until satisfied, but then I want a nice thick coat like you see on Fenders and such. I'm guessing 5-7 coats of lacquer, then three for a clear coat?
I'm gonna go and give the guy some trial piece of various woods to see how well it goes. Everything will be done in a paint booth, I believe we won't need bake curing, 25 degs will be enough for a day or two, then curing on ambient air for a week or so.