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Hi all,

I am (trying to) finish up a humidor I'm working on, which is based on the Wood Whisperer guild plans. I'm attempting a high gloss lacquer finish. This is my first time working with lacquer.

The wood/veneer was sealed with shellac, then pore filled with Timbermate. I used spray can lacquer, a brand from Lowes since I could not find any locally available lacquer for my HVLP gun. I applied 10 coats. I then let the finish cure for about 10 days.

I began the rubbing out process today. I flattened the surface with 320 grit wet/dry sandpaper using soapy water as a lubricant. Following this I used a ROS with Abralon pads at 500, 1000, 2000 grit. It was after this step I noticed a problem. I believe I sanded through the finish. Please see pictures below.

Brown Wood Rectangle Metal Soil


Wood Automotive exterior Natural material Wood stain Bumper


Any thoughts on what to do at this point? I understand lacquer is repairable, should I reapply lacquer just to the affected areas, or to the whole project, repeating several coats again? I can only spray lacquer outside (I don't have adequate ventilation in my below grade shop) and the weather is getting too cold for a good outcome.

I was thinking about brushing lacquer in the garage. It's my understanding that brushstrokes or other imperfections can be taken care of in the flattening process before rubbing out. Should I just brush and rebuild a coat on the bad spots? I'm happy with the finish on the good portions. After building finish on the bad spots I would take the whole project through all of the rubbing out steps again.

Lastly, I think some of the pore fill may have been disrupted during the wet sanding. I'm thinking I'll just pore fill with more lacquer in the affected areas.

Argh, 3 weeks of finishing work down the drain! Thoughts on the best way to repair? Thanks!
 

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You sanded through the finish. Don't use the ROS. Even 10 coats of lacquer is not very thick. When I put on a lacquer finish. I start sanding lightly after the first coat. By hand with a sanding block. I will start with 320 after first coat this knocks down anything that is raised by the lacquer. I will put on 1 or 2 coats a day sanding lightly between each coat. after the 320 I'll go 400 then 600, 1000 and maybe 2000 and then after the 200 I will use rubbing compound before the wax.
I don't know why you waited 10 days the lacquer dries in about an hour or 2. I don't use a filler but there is nothing wrong with using one.
In your case it is going to take some time. I would try to build the finish back up where you sanded through once that is done a few coats on the whole thing to even the finish out. Lacquer is a fairly hot finish and will soften the coat below it and adhere to it very well. Stay away from the power sanders. Use the coarser grits until you get it flattened out the go with the finer grits to get the build up and gloss. The thing I like about lacquer and also hate is it dries quickly so you can depending on temperature and humidity put on more tha one coa a day. Just make sure the what ever you use for lubricant is removed ad the surface is dry before applying the next coat.
You can use the lacquer to fill the pores but it takes a lot of coats and sanding out between coats to get it. Where you used the filler on the rest of the box you may want to apply the same filler to keep the look the same.
I generally just use the finish to fill the pores and sand between each coat until they are filled.
 

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Discussion Starter · #3 ·
Thanks for the reply Bruce. I think you're right about the ROS. I'm happy to know I can still repair the finish.

I did sand after every 2 coats with 320 grit. I let the finish "cure" for 10 days before rubbing out based on information I read about "finishing the finish."

I'll rebuild the lacquer and be more cautious with the final sanding when I get back to that step.
 

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Just a comment about cold weather and lacquer. It will work when the temps are quite low. I've sprayed it outside below 40º and had it it dry. It's an evaporative finish; as long as the solvents evaporate it will dry, and they evaporate at much lower temps than you might think (albeit more slowly). So don't be afraid to spray it outside, what I did was spray outside and wait 15 minutes or so (for the majority of the solvents to evaporate) then bring it inside…you could wait even longer if needed. Of course, that assumes that the cold is the only problem outside, but it's usually accompanied by wind/rain/snow/whatever.
 

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Discussion Starter · #5 ·
Thanks for the tips Fred. It'll be in the mid 50s here tomorrow, so I'll try to make go of spraying outside. Spraying seems a whole lot easier than brushing for lacquer.
 

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Lacquer is one of my favorite finishes. Very forgiving and easy to repair. Remember each coat you spray will soak into the previous coat. If I do a sand between coats I only use those Foam backed Mikron pads 1000 grit very lightly and with mineral spirits for lube. Have never had a problem. Darn nice looking box by the way.

I will use the HVLP spray on 3 coats, wet sand and put on 2-3 more after that for a very smooth finish. If a few nubs I will take 2000 grit Mikron foam pad and rub it out. I myself would never sand between coats.
 

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I use nitrocellulose lacquer for guitar finishing. I find it very forgivable for doing repairs and touchups as it melts into the preceeding coats.

Altho "dry" after a few hours it is best to allow about 3 days between sanding back coats. So you could apply a few dust coats (light mist coats) initially then progressively add fuller coats till you get the desired result.

I usually sand (wet with detergent in the water) initial coats but not between every coat thereafter. Any "orange peel" on the surface will need sanding back & it also depends on how level my prior coats are. Fine polish with car rubbing compounds and silicone free wax.

NOTE: Don't use products containing silicone on lacquers particularly nitrocellulose.

Also nitro & polys don't mix! You can't apply them onto each other. However either can be used over/with acrylics, water based finishes etc but not with each other.

It is worth noting that CURE Time for all "paints" & lacquers is 30 days for each coat. This applies to enamels, polyurethanes and varnishes etc. So after your last coat is applied it will be 30 days before full cure (hardness) is reached. Don't believe me? ...ask a paint chemist but rest assured this info is accurate.

Some acoustic guitar luthiers won't sand until that 30 days has been reached for each coat to ensure maximum hardness before sanding and applying the next coat. The reason seems to be to reduce the chances of cutting thru each coat as they use very thin coats ie in terms of thickness, to produce a superior finish that doesn't interfere with the tone responses of the guitar body.
 

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Discussion Starter · #8 ·
Thanks for the advice Gshepherd and Bilbaggins, very helpful.

So far I've liked the qualities of lacquer excepting the fumes. I figured this humidor would be a good chance to venture farther into the world of film finishes - most of my experience thus far has been with varnish, oil, or shellac. Every finishing process seems to have its idiosyncrasies. I guess it's natural to have some issues my first time around.

I'll redo with lacquer and post the project when it's finally completed.
 

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Your humidor will be saved, looks great btw. Looks like you did everything right except using the ROS. I hate it when I do things like that but at least your project can be spared.
 
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