Respray

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Author Message   Bambusa Username: Bambusa Registered: 9-2007 Posted on Monday, October 08, 2007 - 8:35 am:    Is there anyway to get a super hard finish on a respray paint job? Or does it come down to letting it sit for a week or two to go hard? I'm currently respraying a BC Rich ST (wouldn't want to mess an Ibanez up) in Acrylic. I'm going to use a clear over the top and apply quite a few layers. Will this give me the strength I am after or will it all wear and ding whenever touched?   Guitarwhisperer Username: Guitarwhisperer Registered: 6-2007 Posted on Monday, October 08, 2007 - 9:55 am:    Apply no more than 2 or 3 coats a day, and anything that comes from a spray can is going to require weeks or possibly months to fully harden. Also, you can't spray the coats too thick, or else the outside will dry, trapping the solvents in and not letting them evaporate. Then it WILL take MONTHS and MONTHS to harden, as well as possibly leaving microscopic solvent bubbles under the finish, especially with acrylic since, unlike laquer, once it cures, it's basically inert, so when the outside dries, the solvents can't evaporate out through the hardened layer, the finsih underneath will remain soft, and bubbles may appear. This is referred to as "case hardening" in the biz. Spray them thin, let them dry an hour between coats, no more than 2 or 3 a day. Laquer dries pretty hard, if done right, and is easier to use if you're a beginner. Laquer MAY case harden if you spray too thick, but since it remains soluble, the solvent eventually fully evaporates, leaving the finish hard and durable. Laquer is also easier to polish out, touch up, or repair if necessary. I hope this helps. Above all, BE PATIENT. That's the hardest part.   Ubetcha Username: Ubetcha Registered: 7-2006 Posted on Wednesday, October 10, 2007 - 9:58 pm:    If you want a super hard finish, try Imron. I had a motorhead friend who was doing a '51 Merc rod in maroon Imron. I took over 3 beater Strat & Tele copy bodies & he shot them. You could drop those babies (I did) on concrete & all there was was a little scuff that you could rub out. Too bad they were maroon, what an ugly color for a guitar.   Mr_roadstar Username: Mr_roadstar Registered: 6-2002 Posted on Thursday, October 11, 2007 - 4:35 am:    "Acrylic" can be lacquer or enamel. "Imron" is an old DuPont brand name for urethane enamel. It was originally used in the aircraft industry. Only old school acrylic enamels can "case harden". Then it just requires a quick scuff with some 600 grit to open the surface again. Modern catalyzed enamels cure with a chemical reaction. Lacquer never really "cures". It continues to out-gas and shrink for many years. This is what causes the "crows feet" or "spiderwebbing" on old lacquer finishes. Nitrocellulose and acrylic both suffer from this problem. If you want a bullet-proof finish you've got to use some kind of catalyzed finish like polyurethane or polyester. They are really more plastic than paint. A powder-coat would be really cool, but I dunno if a wood body would take to kindly to the baking process... The Bear   Bambusa Username: Bambusa Registered: 9-2007 Posted on Thursday, October 11, 2007 - 5:08 am:    So in reality - don't mess with the original finishes! I inherited a guitar that had been 'professionally' resprayed and the clear was all flaky and ended up coming off in your hands. I'm still in the primer stage BTW..I plugged up a single coil hole and converted the guitar from SSH to HH..but no matter how well I fill, sand and respray the primer I still get a raise where the middle S was filled. I know the block of wood I used to fill the void is not to high because I can sand the primer back to a very smooth surface with no hint of anything underneath. (the block of wood is screwed in place from behind so it doesn't move, and around the block and under the block was filled with wood putty) But when I re-coat with primer, as it dries, it raises to form the shape of the S hole. It's getting frustrating!! Any advice would be appreciated. One suggestion was that the wood I used to fill is of a different density and expanding under the primer, but when I sand it back every time I never expose any wood!...help   Guitarwhisperer Username: Guitarwhisperer Registered: 6-2007 Posted on Thursday, October 11, 2007 - 8:38 am:    In order to really get a level glossy "factory" finish, you have to "level sand" the finish flat after it cures out, then polish it with rubbing compounds. 3M rubbing compound polish out completely sanding scratches 1200 grit or finer, so if you level sand to 1500 grit then use the 3M rubbing compound, it will be smooth and glassy. Follow it up with Meguiars Pure Polish for that "wet look" After about six months, laquer's about 99% dry. (When people say "laquer, they'reusually referring to finishes that dissolve in laquer thinner, like nitrocellulose laquer. Acrylic laquer is not really laquer, but they call it that anyways.) The cracks and crows feet that develop are called "finish checks" in the biz and are caused by the finish expanding and contracting faster than the wood throughout the seasons. I've seen guitars shipped in the winter time, and when the case is opened too soon after recieving the instrument, while it is still cold, finish checks appeared, in a brand new instrument. This can be compared to an ice cube cracking when you pour water over it. I've also seen 50 year old Gibson guitars with NO finish checks at all. I worked in a vintage guitar shop for over 3 years doing repairs and restorations, so I've seen a LOT of old guitars. The ones with the checks seemed to me to be the ones that were gigged out more, and exposed to more weather. The more brittle finishes like acrylic and laquer can check, usually the polyurethanes (They can be acrylic, polyester, or vinyl, they're all called polyurethane) which is very hard but not brittle, typically doesn't check over the years, since the molecular structure is more plastic and spongy, and can handle expansion and contraction (called "weathering" in the biz) better than acrylic laquer or nitro laquer (acrylic can be both). The downside to the polyurethanes and the catalyzed varnishes (including catalyzed nitro) is the extreme toxicity. One of the deadliest components has no odor, and therefore respirators aren't recommended, since you wouldn't be able to tell when the cartridge was wearing out, so a forced-air ventilation system is required, which looks kinda like a spacesuit. Also the good polyurethanes don't come in spray cans. I've obtained professional finishes over the years with Behlen's Jet Spray laquer. The only time I've ever had the finish flake and come off on me was when I used an incompatible sealer. Lately, I just ship my guitars off to Wilkin's Guitar Finishes and have them do a catalyzed gloss polyester finish on my guitars, they come back perfect. Just search for "wilkin's guitars" and you'll find his web page. BTW, acrylic, polyester, vinyl, these are all just bases. They come in different formulations with different properties, so for instance, a vinyl record will be softer than a vinyl finish, etc. The vinyls and polyesters formulated for the auto industry are extremely hard and durable, and make great guitar finishes. All this is just my opinion BTW so, guys, don't take it too personally if you read something you've heard differently somewhere else. My opinions are coming from personal experience, not a book of someone else's personal experience. Personal experiences have to be interpreted, and can be flawed, no matter who's they are whether firsthand, or read out of a book.

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