# Lacquer damage



## Purrmaster (Sep 1, 2012)

First off, I apologize for the pictures. It was devilishly hard to get a picture of the damaged areas and I don't think it turned out so well.

I just got a coffee table to my girlfriend. I finished the table with Deft gloss *brushing* lacquer. I put on several coats. After the last coat I let it sit for a couple of weeks. Then I rubbed the finish out using sandpaper and mineral spirits. I let it set another couple of weeks, possibly more.

Everything went fine until we got pizza. We put some pizza boxes on the table. When we lifted the boxes there was what looks like damage to the lacquer. There are patchy areas of dullness anywhere the pizza boxes were. It's as if someone spilled some lacquer thinner on there or it was sanded with 220 grit sandpaper.

Water spots have not been a problem. The finish appears to be water resistant. I even tested it with orange juice to see if acids would eat into it. Nope.

I thought at first it might be the coat of wax I had put on there melting. But I've rubbed and rubbed at these spots, including water and spray cleaner. Made no difference.

It would appear the lacquer has been damaged. But I don't see how. I gave it plenty of time to cure before rubbing and even more afterwards. I have finished other stuff with this lacquer and the other stuff isn't giving me a problem. In fact, there's another table I made with Deft brushing lacquer. It went through the same regimen. I put the pizza boxes on it for destructive testing. It's perfectly fine.

Does anyone have an idea as to what's going on here? I can always brush on another coat of lacquer but I want to know if this will haooen again.

It's supposed to be a workaday coffee table. It should be something that doesn't have to be handled delicately. It should able to take use and some abuse. I realize nitro lacquer isn't as tough as polyurethane but it's pretty durable. And the majority of factory made furniture is finished with lacquer.

I took some digital pictures. The damage can only be seen in a raking light and so it's difficult to make the damage out. I tried to point it out but it's still hard to see. But to the naked eye it's extremely obvious. I can even feel the roughness.

My assumption at this point is that the heat damaged it. What happens when she puts a hot coffee cup on her coffee table?

Insight would be appreciated. Thank you.


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## Wildwood (Jul 22, 2012)

You can spot repair the heat damage. You need coasters, potholders, or trivets to protect from heat damage for most penetrating or clear film finishes. Yes, some finishes might prove better than others preventing heat damage. Just not sure which ones.


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## BillWhite (Jul 23, 2007)

I TOLD you that danged pizza would eat your insides. Just look what it has done to that nice table.
(Did that sound like your Momma?)


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## tefinn (Sep 23, 2011)

I'm with Wildwood on this one. It was the heat, not the box. Heat will damage pretty much any clear top coat if hot enough or left on long enough. In your case, because it was so new, it didn't take much to damage it.


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## Finisherman (May 3, 2013)

I agree with the above posters. You're looking at a case of heat damage here. Nitrocellulose lacquer, which is what Deft is, is especially susceptible. The good news is that it's almost as easy to repair. Clean off the wax you applied with either mineral spirits or naphtha and a soft cloth. Sand the damaged area lightly with something like 400 to 600 grit paper and then simply spray or brush another coat of lacquer over the table top. An aerosol can might serve you well in a situation like this. By the way, in the future, you might consider foregoing the wax. It doesn't provide much extra protection, and it can cause headaches for future refinishers. Just my two cents.


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## pintodeluxe (Sep 12, 2010)

I cannot imagine a boxed pizza being hot enough to damage lacquer. I have used a lacquered table daily for 5 years and it looks like new. I have used Deft, Valspar, and Magnalac all with excellent results.

I have never heard of sanding with mineral spirits to rub out a finish. What grit did you use?
I feel like the finish may have been damaged in that step of the process. 
I usually scuff sand between coats with a 300 grit flexible sanding sponge. I have seen many "fine grit" sanding sponges that are way too coarse for finish work. To rub out a finish I prefer waxing with #0000 steel wool.

At any rate it should be repairable with another topcoat. 1+ Finishermans suggestion to clean the wax off with mineral spirits. Any remaining wax will cause fisheyes in the topcoat.


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## Purrmaster (Sep 1, 2012)

Thanks for the responses. It raised a few more questions.

First off, I'll give you the finishing schedule. I stained it with Minwax stain. Let that dry for a few days after I couldn't smell the mineral spirits anymore. Slapped on one coat of Deft's matching sanding sealer. Let that dry overnight, sanded a little and then went to town brushing on the lacquer. After the last coat (I did several coats over several days) I let it sit for a couple of weeks to dry and harden.

Then I rubbed it out which consisted of starting with 400 grit paper (dry). Then I moved to wet or dry papers, using mineral spirits as the lubricant. I tried using water as a lubricant on this lacquer before and I ended up sanding through the finish. And water got into the wood and it was a mess. Since then I've used mineral spirits with no issues.

My sanding sequence was 600-800-1,000-1,200-1,500-2,000-2,500. Followed by Turtle Wax (automotive) rubbing compound, then polish, and then Meguiar's swirl remover. Then top coated it with Minwax paste finishing wax. This is not the best rubbing out method ever but it gives me decent results that are repeatable. With lacquer, that is.

As I said I think you guys are right: It's heat damage. But from a pizza box? The pizza box wasn't that hot. Not as hot as a plate of hot spaghetti or a cup of hot coffee would be.

I know lacquer isn't as tough as a varnish, whose molecules cross link. It's kind of mid way between varnish and shellac.

My understanding is that the vast majority of furniture you buy at the store is finished with nitrocellulose lacquer. It dries fast, sprays well, and can be recoated at any time. And I've never seen this kind of damage from a pizza box on commercially produced tables.

I suppose it's possible the lacquer isn't fully dry and hardened. But a month would seem to be long enough with lacquer. Even a brushing lacquer, which dries more slowly than spray lacquer. I think I even looked up the time for a full cure and it was something like 7 days (I could be wrong). And I've read that the "smell test" is a good test of whether the finish has cured or not. I didn't smell any lacquer thinner when I rubbed it out and I don't smell any now.

Thankfully, as was pointed out, lacquer is repairable. I have a rattle can of the Deft that I'll probably use for a couple of recoats. I don't want to have to rub it out again. Mainly because that will require dragging it back to my shop which is probably not possible at this point.

Is this kind of heat sensitivity simply to be expected with lacquer, then? If so, what about shellac?

Thanks.


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## tefinn (Sep 23, 2011)

I don't think you did any thing wrong with your finishing steps. I do think the finish hadn't completely cured though. With spray lacquer (can or gun), the layers you lay down are much lighter and dry and cure quicker. By brushing it on, you have thicker layers that take longer to cure. The more you put down, the longer that time is. What most likely happened was the surface was more cured than under that top layer (kind of like candy with a hard shell and soft center).

When you put the warm box on top it helped the surface soften back into the lower layers of uncured lacquer. Your older pieces have had more time to cure and you can't really compare any of them to the factory made pieces because of the way they are done.

If you want to try using water again when rubbing out a finish, make sure you add some liquid soap for lubricant.


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## JAAune (Jan 22, 2012)

I rather doubt that most commercial furniture is finished with nitrocellose lacquer. It's far more likely that they use either a precat or a post catalyzed finish. Both of those are more durable than the nitro so that would do a lot to explain why you never see this kind of damage on those products.

The post catalyzed finishes are especially useful in a production environment because they cure more quickly than lacquers and they are far more durable. They aren't so repairable but that's not an issue for most companies because they know they'll never have to repair anything.

One minor detail to consider is that brown paper (and therefore cardboard) are abrasive. If you were sliding the pizza box back and forth it's possible the combination of heat and abrasion dulled the finish. I actually use brown paper as a tool in my finishing kit if I want to alter the sheen of a topcoat.

Don't forget the grease issue. Pizza boxes tend to soak up a lot of grease and moisture. You therefore had a warm, greasy, damp and abrasive object sitting directly on a finish which isn't nearly as durable as commercial topcoats.

Top that off with Tefinn's observation that the finish was probably not fully cured (the precat I use seems to reach full cure in 3 weeks at 70 degrees) and you can see there's plenty of potential for things to go wrong.


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## pintodeluxe (Sep 12, 2010)

All the lacquers I use are pre-catalyzed. Light abrasion, a little heat or moisture are non-issues for pre-cat lacquer. My application method has always been spraying with HVLP.

Could it be a defective can of lacquer?


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## Purrmaster (Sep 1, 2012)

As much as I'd like to blame the lacquer for this, I think it's my fault. I suspect you guys are right: The finish didn't completely cure. So the question is: How long will it take for it to cure? And how do I know when it's cured enough for standard use? As I said, there was no solvent smell. It rubbed out fine and sandpaper is more abrasive than a pizza box.

I also wonder about the chemicals used in making cardboard. I think paper manufacturing often uses some pretty nasty chemicals. While I doubt a pizza box is oozing chemical death, do you think it's possible there's enough chemicals left on the material to (along with the heat) soften the finish.

Can you get pre-catalyzed lacquer for brushing? I don't have spray equipment, won't have it any time soon, and don't have a place to spray. So I'm stuck with rattle cans (which get expensive fast) or brushing.

You're right, of course, that brushing on the lacquer will put on heavier coats than spraying. I did thin the brushing lacquer some, but I suspect it was still much too thick for a spray gun.

It also causes me to wonder what I would do if I ever wanted to sell a piece. I would think a customer would be turned of by being told: "It'll take 3 months to make because I have to let the finish sit for a month before you can use it". Thankfully I have no plans to sell my furniture.


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## pintodeluxe (Sep 12, 2010)

What did you thin the lacquer with? Only lacquer thinner hopefully.

My lacquered projects are always ready to use in 1-2 days.


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## tefinn (Sep 23, 2011)

I don't think you have to worry about chemicals in the box. It was mainly the heat and as JAAune added, the moisture and possibly the grease too. A bad combination for any finish.

If you were planning to build to sell, I'd use a good quality solvent poly on your tables. It's always better to spray, but since your not set up for that, you can get pretty much the same results as the lacquer by brushing on poly. The poly is also more durable than lacquer and you only need to put on 3-5 coats. If you rub it out the same way as in your OP, go with at least 5 coats. I'd also use soapy water for the rub out lube.


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## Purrmaster (Sep 1, 2012)

I did indeed only thin with lacquer thinner. I keep some around for thinning and cleaning brushes.

I guess I'll have to reserve the lacquer for more decorative stuff. That's too bad, considering I just bought a gallon of Deft for fear they were discontinuing it.


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