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I need to add some coats of lacquer to several instruments that I started spraying several years ago but didn’t complete. Do I dilute the lacquer more than usual? Any advice would be greatly appreciated.

Lacquer should burn in, but on well-dried finishes as well as lightly-contaminated surfaces, toothing the existing finish aids uniform burn-in, and a 50/50 thinner-heavy flash coat with perhaps 5% added butyl cellosolve or lacquer retarder will push some VOCs into the older material and encourage a deeper burn-in without wetting things such that any separation from the sealer will occur. The mechanical abrasion can be accomplished with 0000/maroon non-woven abrasive pads with care taken to get a uniform matte appearance and minimal dried material removal over the entire area to be over-coated. This process will also free any contaminates (skin oils, dirt, airborne contaminates), so clean the surface with naphtha after abrading to remove the abrasive grit/debris, powdered lacquer, and any oils/waxes from handling. Fresh nitrile gloves help keep things clean.

The flash coat should be a just-wet-enough coat applied such that it will not run... it will not hang like a 70/30 or 75/25 wet coat, but it is essential to avoid too dry a coat if you want adequate burn-in. Once that coat fully flashes off, further top coats can be applied with normal thinning of instrument lacquer.

Another thing to consider is where the over-spraying will be terminated if not doing the entire body, neck or assembled instrument. If just adding a few top coats, prep top and top bindings, then mask the line between binding and side... spray the top such that the fan blows off the top much as we buff edges... that gets some lacquer blend onto the bindings, but minimizes the hard edge and ensuing scrape/sand/buff work.

Good advice from Willard. I suggest using the same brand if at all possible, and asking your paint dealer if the company made any changes in the formula since the original lacquer was laid down.

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"Act your age, not your shoe size" - Prince

Thanks, guys. Really appreciate the detailed advice. Just what I needed.
BTW…reminds me once again why I appreciate this forum so much.