Polishing Nitrocellulose Lacquer
It's hanging and drying - How do I polish it?

Kevin Birmingham - 08:13am Jan 11, 1999

Hi, it has been a while since I posted a message. My first project is almost completed and it's success can be largely attributed to the information that I have gathered from this site. Thank you. I have sprayed nine coats of nitro laquer on my electric guitar and it is hanging up and drying for the next three weeks. I have read a lot of info on the polishing phase, but I still have some questions. I have wet/dry sandpaper up to 1500, but I can't find anything finer around Toronto. Do I need to go finer? Is there a source for finer paper near me? Can I use automotive compounds? Canadian Tire has Turtle Wax brand Polishing and Rubbing compounds. Can these be used? I don't have a buffer, so I will probably be hand polishing. Any suggested appoaches? Thank you. Kevin.

Kevin, you don’t have to use finer grit paper if you are going to use a compound like 3M Finesse fine cut cleaner or Meguires fine cut cleaner. These compounds will remove 1200 grit scratches. The type of pad you use to apply the compound with makes a big difference in the results. A coarse pad will leave scratches that a fine cloth would not leave. Follow with a swirl remover. I like to take it another couple of steps beyond this level with the dry compounds that Stew Mack has using a power buffer.

Kevin, have you thought of Micro-Mesh? In Canada, Lee Valley carries it, as does Timeless Instruments. It's reusable, washable, and can be used without any lubricant except for a few drops of water.

Thanks. Two questions. 1) Does anyone know where in the Toronto area I could get 3M Finesse fine cut cleaner? 2) Lee Valley isn't far from me. How far can you go towards getting a high gloss finish with micro-mesh? Would I still need polishing compounds?

Kevin,

If you use the micromesh all the way up to the 12000 grit, you'll have a nice gloss. After that, if you polish with the dry compound that Stew-Mac sells, you'll have a mirror. If you're on a budget, you can use your electric hand-held drill motor with a buff with the dry compound.

The 3M product is often found at auto parts stores.

I have just sprayed 2 coats of laquer over 3 coats of sanding sealer on a quilted maple electric guitar body and now notice a few small white specks which appear to be under the top finish. Any solutions other than sanding back through?

John,

It's probably dust or some other foreign matter. As far as I know, mechanically removing it is the only way. You may be able to dig them out with a #11 x-acto blade. Then just fill the little hole with laquer drops. You could also take a tiny drill bit - say a #80 or one just big enough to obliterate the specks, and using your fingers, drill the spot. The hole is so small that once filled, you'd never see it.

John are you talking about nitrocellulose lacquer? It could be dust as Dave says, or it could be some other problems. Lacquer sanding sealer contains stearates and if you don’t mix it well and strain it you risk getting “chunks” of this material into the finish coat this can cause white specs. If you are shooting satin or eggshell or dead flat lacquer there is a flattening agent that collects at the bottom of the can. When it is at the bottom of the can it look clear but if you stir it up and you don’t strain it you will get chunks in your gun. When this “clear” material is shot through the gun and it dries it turns white and you get these white spots all over. The other thing that can happen is pinholeing. Very small bubbles could have formed in the sanding sealer coats that were sanded through opening the bubble. When the sealer was sanded white sealer powder was trapped in the bubble and the topcoats never had a chance to penetrate through the dust leaving a white spot. Pinholes can be caused by shooting over a surface that is warmer than the lacquer, applying heat to the lacquer after it is shot if both the lacquer and the surface are cold, too much thinner, too little thinner, too much air pressure, too little air pressure, moving the gun too slow, getting the gun too close to the surface being shot. If you have pinholes near the surface you may be able to get them out by spraying thinner over the top which will melt through a few layers and hopefully release the trapped air. You can try mixing a tablespoon of retarder in with a pint of the thinner if thinner alone does not work. If you are using water base lacquer forget whatever I said as I dont know anything about that.

Any other suggestions? BTW# Belehns blush remover is handy as it comes in a bomb can so you dont have to empty your gun.

I am preparing for my final polishing and buffing of the nitro finish. This is what I am going to try. Any opinions?

The guitar was hung to dry for two weeks and then I sanded it with 800 until almost totally smooth. My plan after another week of drying is:

1) sand with 1000, 1500 (couldn't find 1200) and then 5 micron (from Lee Valley) - I think it is like 2000

2) Use a buffing wheel made with flanelette - a) red compound (CDN Tire), then b) White Diamond compound (Lee Valley)

3) final polish with Maguier's second step (it is part of their three step car polish - the last step is wax). Is this going to work???

Thanks again, Kevin.

If you are going to use the red compound there should be no need to sand beyond 1500 in fact you might be able to get away with the 800. I would go with Meguires fine cut cleaner after the red then white stick compound. But then I don’t want to be responsible if this is your first attempt at a rubout.<g> There are a lot of ways to do it. Once you have it to the white compound putting a wax like final polish is just going to smear it up. You will probably have some wax buildup from the buffing stick that will need to be removed by something like Meguires final inspection.

Any wax buildup could easily be removed with mineral spirits or naptha.

This has been quite an adventure trying to put together a process for rubbing out the finish. There are almost as many methods and definitly as many opinions as there are people doing it! It has been suggested to me that using a buffing wheel is too aggressive. That I can end us putting grooves in the finish. Any suggestions on using a buffing wheel? I am determined to use the wheel I made (I spent too many hours cutting up flannelette into circles).

Meguires' products are labeled differently here at Canadian Tire, then in catalogues like Stew-Mac. The product I have is the one just before the one with wax in it. It has been suggested that I use another Meguires product that is equivalent to red instead of red. So my process would be to go to 1500; then Meguires liquid rubbing; then white and finally the Meguires polishing. Then again I am beginning to think that Satin would be a nice finish!!!!! After the final polish should I use something like Martin Guitar polish? Thanks, I really appreciate this forum!

PS What is "Prepare to abandon ship" about???

Don’t use Martin guitar polish on a black instrument it will leave smears all over that you wont be able to wipe off. You can put ripples in the lacquer with a buffer if you bear down too hard. I use fairly high speed with very little pressure. Do not get the leading edge of the instrument into the buffer or it will grab it and through the instrument to the floor, at best you will only burn through some finish on the edge. Mineral spirits will even work for wet sanding as it lubricates better than soapy water; it also has fewer tendencies create checks or swollen spots in any holes that were drilled before finishing like soapy water will.

My experience bears out what Jason said. I now use mineral spirits for wet sanding. No more problems with cracks around screw holes. I do wear my organic vapor mask while wet sanding now, but so what. The mineral spirits wet the sandpaper very quickly too - no need to soak overnight like you should with water.

Note, though, that the Micro Mesh stuff doesn't like mineral spirits very well - at least not the random-orbital sander pads. They delaminate (abrasive from velcro) if you get mineral spirits on them. I still use MicroMesh with soapy water for wet-sanding "touch up" work. I just have to be EXTREMELY CAREFUL about screw holes, etc.

Michael

Most of the manufacturers are no longer wet sanding their finishes. They are using the 3M microfinishing films, dry. They start with 30 micron film and go up from there, all with a dynabrade or similar outfitted with a flexible replacement pad that allows them to get into tight waists and cutaways. Cutaways still require some hand work. Steve Henderson tells me he sands out a guitar in less than 15 minutes and then goes to the buffer. The sanding film prevents all the problems of getting moisture where you don't want it -- tuning machine holes, soundhole, neck bolt holes, etc. After sanding they go to red and white dry menzerna compounds.

I will be checking into it after I get a few things done that are on my schedule, it gets crazy around here (Seattle) at times. I don’t think I will try it on an instrument right off and the rotary tool will have to be purchased. I am sure it takes a little technique to do it right any way last time I said I would check out a finishing item it took over a month before I got to it so if someone else gets to it first post it. 15 minutes sounds exciting maybe we are getting our legs pulled a bit? It must take an hour to level the finish even with the power sander. 15 minutes really?

Let me preface this continued discussion by saying I haven't tried this yet. I was chatting with Steve last week about some lacquer cracks and that led to related areas such as sanding and unrelated like frisbee golf.

Here's some of the reason for the faster sand out. We wet sand, not to improve the cutting ability of the sandpaper specifically, but rather to do so by preventing the sandpaper from clogging. The problem is when you lubricate, be it soapy water, naptha, or mineral spirits, you effectively slow down the polishing process because you've made the surface slick. The same action that lubricates the paper and prevents it from clogging, interferes with the ability for that paper to cut.

The advantages of the dry sanding are that you don't have to worry about the finish lifting, getting messy water inside your nice clean body. If you sand through, none of your lubricant will contaminate your surfaces.

As I said, Steve will be back next week and I'll get a schedule and we can talk more about it then. Same bat station....

I have noticed that wet sanding with mineral spirits is more aggressive than “soapy” water.

Jason, that's due to the surfactant (the slippery stuff) in the soap. Mineral spirits have none.

Another advantage of dry sanding is that you have a better idea of the progress you're making. I always think my wet surfaces look great, then I realize I was fooling myself once they dry.

Yes you have to wipe them dry all the time to see what’s happening, maybe that’s why it takes so long to level a finish.<g> I think there is more to the aggressiveness of mineral spirits than the lack of surfactant content. I have noticed that you can leave a “burn” in the lacquer if you get a big drip that you don’t wipe off. Any one else seen that? You can see where the mineral spirits were; kind of looks like a welt. I suppose I could go call a chemist but I have almost used up my allotment of free advice.

Hi,I have two more questions.

1) I started the process of polishing the finish last week, but after doing two steps with Mcguires the finish was soft enough to leave finger prints. My Nitro finish has been drying for three week already. I have left it another week and will try again tomorrow. Is this normal? I didn't use any retarder in the nitro, just thinner.

2) Next week I will be redrilling the holes that I had already drilled (I filled them with wood filler before finishing) and I will be drilling a couple of new ones). Any tips or tricks to this. I don't want to chip or crack the finish. Thanks.

It’s not the Meguires making it soft. I often let the instrument sit for a couple of months before buffing. If I am doing something like a Tele that has ferrules where the strings go through the body I buff it out after 3 or 4 weeks while the finish is still soft so when the ferrule holes are drilled the lacquer doesn’t chip. Don’t hold the instrument tightly while buffing you can see why. Be careful about what you lay it on while doing assembly or you can get imprints. I always pick the instrument up every 10 minutes to help prevent this from happening. I have seen fingerprint disappear after several months as the finish is still plasticised, don’t count on it though. Use sharp drill bits keep the standard sizes you use separate from your other bits and only use them for lacquer. Lacquer hardness appears to differ in timeline depending on how many coats were applied, how fast and the ambient temperature during curing.

Okay, Okay. Here it is as promised. I just chatted with Steve Henderson and here's their sanding regimen for their finish:

They use the 3M Imperial Microfinishing film abrasives and a Dynabrade for all surfaces (one of the sanders is fitted with a soft pad so that they can sand into the waist and cutaways). They use 30, 800, and 1200 Microfinishing films and then buff out with fine and extra fine Menzerna, followed by a clean wheel buff to remove any remaining residue. The films are used DRY. No more wet sanding, folks. And its fast. Please note that the 800 and 1200 are grit equivalent; Steve couldn't remember the exact numbers.

From our nation's receptacle....

David,

Thank you for the information... I have several grades of the 3M microfinishing film and polishing pads, and if I read the information comparison chart correctly, 30 micron is 360 grit (I'm using the ANSI chart), 15 micron = 600 grit, 9 micron = 1000 grit, 3 micron = 1500 and 1 micron = 2000 grit. I hope this is correct.

Gary, you're way ahead of me. My 3M supplier doesn't carry them, so I gotta order that stuff. Bruce Nelson, at 3M's technical 800 number, which is on my rolodex at the office, (I'll add it later) said that the soft pads that Breedlove is using on their Dynabrade is only available for air driven tools; however, 3M makes interface pads and so forth that could be combined to give a similarly soft foam backing that would allow the rest of us electric 5" sander folks a way of doing similar work.

Mike, I have found a ready supply of micro abrasives and automotive paint supply stores. Check your yellow pages under paint.

In perusing the LMI price list I found they have it in both 8.5 x 11 sheets as well as 5" and 6" PSA disks. They have it in 30u (400), 15u (500) and 9u (1200) grits. I'm going to see if they could start carrying the 800 grit equivalent as well as the 3M interface pads. These are spongy pads available with a PSA to PSA interface, hook-it to hook-it, hook-it to PSA and PSA to hook-it. Breedlove uses these things to allow them to sand into the waist with a Dynabrade.

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