jlarremore Posted March 19, 2009 Report Share Posted March 19, 2009 I just went through re-finishing a guitar with flames. Coats of color and probably 20 coats of poly. Sanded from 320, 400. 600, 800, 1000, 1500, 2000, rubbing compound and polish. Still no mirror finish. What did I do wrong? I don't get it. If I finish a guitar without paint it works out great. MIRROR finish. Jef Quote Link to comment Share on other sites More sharing options...
ihocky2 Posted March 19, 2009 Report Share Posted March 19, 2009 What type of poly did you use? How much time between coats? How long did you let it dry before polishing? 320 is rather coarse to start your final sanding on. It cuts very quickly, but leaves scratches that are harder to remove. I don't start below 600, and try not to start below 1000. Quote Link to comment Share on other sites More sharing options...
Bmth Builder Posted March 19, 2009 Report Share Posted March 19, 2009 Isnt 20 coats of poly rather thick? Isnt it in danger of cracking after about 3 coats? Quote Link to comment Share on other sites More sharing options...
DGW Posted March 19, 2009 Report Share Posted March 19, 2009 What type of buffing compounds are you using? And are you doing this by hand or on a wheel? Quote Link to comment Share on other sites More sharing options...
jlarremore Posted March 19, 2009 Author Report Share Posted March 19, 2009 I'm using 3M rubbing compound and Turtle Wax polish. Neither my preference. I can't find the 3M finesse it. And I am using a buffing wheel and some of the papers by hand. Time between thin coats is not more than 2 hours. Quote Link to comment Share on other sites More sharing options...
DGW Posted March 19, 2009 Report Share Posted March 19, 2009 (edited) I'd recommend Menzerna compounds for use on a wheel. http://www.stewmac.com/shop/Finishing_supp..._Compounds.html Works really well for me. Edited March 19, 2009 by DGW Quote Link to comment Share on other sites More sharing options...
Narcissism Posted March 19, 2009 Report Share Posted March 19, 2009 Poly really shouldn't be sanded until after at least a day... If it doesn't feel like an expensive glossed over table, then chances are that it isn't dry yet. I normally do 2 days between coats, just to make sure. Even if the coats are thin and your poly says (cures in under 2 hours) you should still give it at least 24 hours before treating it like its solid. I stood mine up verticle after 4-8 hours, and a few hours later i noticed it was developing waves on it. Turns out it was very slowly running. Quote Link to comment Share on other sites More sharing options...
Tim37 Posted March 20, 2009 Report Share Posted March 20, 2009 i don't know much about wood finishes but on a car if you built up 20 coats of clear that fast you would have to worry about solvents building up and clouding the finish Quote Link to comment Share on other sites More sharing options...
ihocky2 Posted March 20, 2009 Report Share Posted March 20, 2009 That is a big reason I asked what kind of poly he used. Minwax in a spray can acts much differently than automotive poly's. 2-part poly's can be polished in 24 hours. Rattle can poly's need at lesat a week until they can be polished. The fingernail and nose test are always good ones. If you can dent it when pressing your finger nail, or still smell the solvents, it is not ready to be polished. The other question is what kind of paint is this over, there may be compatability issues? Quote Link to comment Share on other sites More sharing options...
jlarremore Posted March 20, 2009 Author Report Share Posted March 20, 2009 The paint is a rattle can enamel over an existing poly finish. Can I re-spray with poly and start over? Quote Link to comment Share on other sites More sharing options...
westhemann Posted March 21, 2009 Report Share Posted March 21, 2009 Here is the thing...it is very difficult.always. So make some flat(and I mean flat) pieces of wood...about 6" by 6"...get duifferent finishes,and try them all(following the methods in the tutorials) make sure you do the work right...and before you know it,you will figure out what works for you...then you just havbe to do it on a guitar,which is harder still.. there are no easy shortcuts. Quote Link to comment Share on other sites More sharing options...
Southpa Posted March 21, 2009 Report Share Posted March 21, 2009 (edited) The paint is a rattle can enamel over an existing poly finish. Never mix coating types ie. lacquer, polyurethanes, enamels etc. or even in a lot of cases (my experience), brands of coatings, especially in the lacquer (nitrocellulose or acrylic) categories. I like doing with automotive paints because there is always a matching primer, color and clear, basically a kit where all the components are MADE TO WORK WITH EACH OTHER. Its a no-brainer and you can't go wrong if you follow instructions and provide the proper conditions. Some enamel DOES NOT POLISH WELL and even if you can get some sort of shine it will be dull in about a month. If applying a coating over poly then the poly must be scuffed well to provide a good bonding surface and to avoid any adherence problems. I mentioned compatibility issues between paints and that is the problem. When doing this the results can be unpredictable. You don't know if the solvents in the new coating will react with the existing coating. And as far as timing goes. I have only one thing to add. The longer I wait the better I feel about the results. This is where aLOT of patience (and restraint ) is needed. When I shoot a guitar now I just let it hang and forget about it for a while. The paint might 'seem' cured, will sand well without clogging the paper AND pass the fingernail test with moderate pressure. But its a real drag to see the nice imprint the towel made in the finish after laying the guitar down for only half an hour! That won't happen again! Edited March 21, 2009 by Southpa Quote Link to comment Share on other sites More sharing options...
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