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Buffing thru Lacquer & Stain Shelf Life

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Forum topic by ronlatour posted 05-31-2019 02:55 PM 331 views 0 times favorited 13 replies Add to Favorites Watch
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ronlatour

12 posts in 142 days


05-31-2019 02:55 PM

Topic tags/keywords: lacquer stain sanding thru finishing

There are 2 issues with this question. I apologize in advance for being somewhat long winded.

1. In preparation for spraying my walnut box with Minwax aerosol lacquer, I consulted this blog about whether to sand between lacquer coats or wait until the last coat. One of the concerns expressed about sanding between coats is the potential to sand thru the finish. There weren’t suggestions as to what to do if that did happen.

In any case, I decided to wait and sand until after the last coat. All went well until I was buffing out the wax. I used a new larger diameter buffer and managed to buff thru the lacquer down to the stain in several areas – bad enough that I’ll have to respray as a minimum. This has never happened to me since I started using lacquer. And I realized that this problem is or will become exactly like the concern expressed about sanding between coats.

The main question is how to surface prep ahead of respraying. My current thinking is to wipe it down with mineral spirits to remove the wax. Then lightly sand with 320 to 400 grit to roughen up the surface trying not to sand into the stain but fully expecting to do so. If I do, I will touch up those areas with more stain. Then vacuum and wipe it down again with mineral spirits to clean away the dust and any residual wax. At that point, I will begin respraying as before and put on at least 3 coats.

2. Now for the 2nd question. Thinking about the solution to the above, I began to wonder about the General Finishing oil-based Honey stain I used. It is 12 years old but still looks and behaves as a good stain. It applied and dried normally. Plus, I sealed with a coat of aerosol shellac. Hence, I didn’t give its shelf life a second thought. GF doesn’t want to be contacted as best as I can find on their website so the question for this group is: Does this stain have a shelf life and could the age of the stain have anything to do with the first problem? And if so, that would mean sanding down completely and starting from scratch.

Thanks ahead for anybody willing to offer help,
Ron


13 replies so far

View Rich's profile

Rich

4832 posts in 1071 days


#1 posted 05-31-2019 03:46 PM

There’s no reason to sand unless you have an uneven surface. The lacquer you spray will amalgamate with the existing lacquer. That way there’s no risk to the stained surface.

Yes, you need to clean off the wax. I prefer naphtha or turpentine over mineral spirits because today’s “low odor” MS is weak.

I’m surprised you were able to buff through the lacquer. How many coats did you do? Aerosols like Minwax generally don’t have the solid content of something like a Sherwin Williams product, so you’ll need many coats. If getting a sprayer isn’t an option, at least look into Mohawk brand aerosol cans. It’s a far superior product compared to Minwax. If you need sources for it, let me know.

When I’m finishing something like a cabinet, or the legs and aprons for a table, I use 4 coats. I spray the first three, let it cure for an hour or two and then sand lightly with 400 before spraying the final coat. The final coat is lighter too.

For a table top I will spray 10 to 12 coats, sanding lightly every few coats. I then wet sand with 400 and up. The final grit I stop with depends on the sheen I’m looking for. I then buff it with pure carnauba wax.

Also, a de-nibber is invaluable for lacquer, as is an ultra thin cabinet scraper with a square edge (don’t burnish to turn a burr). It’s far better to plane off any imperfections than to sand. I only sand once the surface is perfectly flat.

-- There's no such thing as a careless electrician

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Davevand

126 posts in 1318 days


#2 posted 05-31-2019 03:49 PM

I am not a finishing expert, but I use lacquer a lot. I never sand between coats unless I need to remove some imperfections, lacquer, like shellac redissolves the finish and creates a single coat of lacquer. Poly needs to be sanded between coats because it is a film and each coat is a separate film built up for the finish.
My go to finish is 3-4 light coats of shellac (no need to sand between coats) let dry for several days, sand smooth, then 5-6 light coats of lacquer, again no need to sand between coats. Lets this dry for several days before I buff it out.
What kind of wax did you use? Silicone in it? If so it will be very hard to get all the wax off and will cause fish eye in your finish. I would wipe it down several time with mineral spirits then sand the finish well and start over with shellac.
If the stain dried completely, it should be fine.
The way I test an old finish is to put a few drops or wipe some on a piece of glass, let sit over night. If it dries and is hard I will use it, if it is soft or not dried I toss it.

View ronlatour's profile

ronlatour

12 posts in 142 days


#3 posted 05-31-2019 05:39 PM

Rich/Davevand, thanks for the quick. To answer some of your questions:

1. I sprayed one coat of shellac and sanded.

2. The box is walnut cremation urn. I sprayed 4 coats of lacquer, sanded, rubbed down & waxed. I spray only a couple times a year in my workshop which is part of my home. When spraying, I have a method to isolate the shop and exhaust it.

3. Obviously, I also was surprised at buffing thru the finish and, as stated, never had this experience before. I use a 1/4”Dia flexible shaft carving hand piece to mount the buffer which is foot controlled & can go up to 26,000rpm. Although it is difficult to keep at a constant speed, I try to keep it at less than half way. I normally use a 4” dia buffer but tried a new 5” dia. It worked fine until I decided to try to get into a shallow rabbet by turning the buffer on edge. I believe that higher tip speed and my lack of control produced the result.

4. I was using an aerosol lacquer from Watco and then Behlen, both satisfactory. I live in Baton Rouge, LA and can only find Watco, Deft and Minwax locally. When I used Behlen, it was mail order. But you can bet from now on, it will be Mohawk or Behlen which I now see are both owned by the same entity – Mohawk or vice versa.

5. The wax is Black Bison & silicon free. I use it solely because it is a wax that takes a high speed/hard pressure buffing to produce a great finish.

6. I will have to buy some Naphtha.

Thanks again.
Ron

View Dark_Lightning's profile

Dark_Lightning

3533 posts in 3591 days


#4 posted 05-31-2019 08:21 PM

It’s been covered pretty well by the first two worthies, but I would offer that I never power-polish wax on a project. It takes more time, but avoids burning through. How big is your project?

-- Steven.......Random Orbital Nailer

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Davevand

126 posts in 1318 days


#5 posted 05-31-2019 10:58 PM

Is your shop climate controlled? I live in Houston and this time of year I spray in the shop and bring the project in the house to cure, leaving it in the shop will take a long time to really cure with the high humidity.

View ronlatour's profile

ronlatour

12 posts in 142 days


#6 posted 06-01-2019 02:25 PM

Dark_Lightning/Davevand, answers:

1. The project is a cremation urn about 10” square x 5” high. I know I could do by hand and now that I realize what trouble I could lead myself into, I will figure our away to avoid in the future. I’m a 78yr old male retired engineer who does this as hobby on consignment. I can only do about 2 boxes/yr.

2. My spray area is in my workroom which is a large connected room to my home. It is air conditioned. When I spray, I isolate the room, keep my window unit running, circulation fan running, & vent the spray hood to my attic using my 6HP shop vac to exhaust the hood. Yes, I know that there is a potential danger to running the fumes thru my vac. So, I avoid this by making an educator out of my vac so the exhaust doesn’t go thru the vac.

Thanks to both of you,
Ron

View Rich's profile

Rich

4832 posts in 1071 days


#7 posted 06-01-2019 04:07 PM

Ron, the sort of polisher you used is really not the best choice for buffing out a finish. If you have it in your budget to spend a little over $100, check out a Porter Cable 73xx sander/buffer/polisher. It’s a very versatile tool that can do aggressive sanding, wet sanding with Abralon pads down to 2000 grit and higher, it has buffing and polishing heads available as well. Its variable speed motor covers any sanding/polishing situation.

It’s what I use on my table tops. As I described above, I start with 10-12 coats of gloss lacquer (you’d need more with aerosol) and then wet sand starting at 400. When I achieve the sheen I’m looking for I apply carnauba wax and put on the wool buffing pad and buff away. The dual action gives a virtually swirl-free finish.

Home Depot sells the model 7346. It comes with a 6” peel and stick face. It’s much better to swap it out for a hook and loop option which you can do for a few bucks on Amazon. The unit accepts any 5/16-24 attachments.

Also, you mentioned an interest in Mohawk lacquer. Westlund Distributing sells it for an excellent price (under $6 per can) and they carry the full line—pre-cat and regular nitro-cellulose, and in all of the sheens from dead flat to gloss. Shipping is a flat rate and is very reasonable.

-- There's no such thing as a careless electrician

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ronlatour

12 posts in 142 days


#8 posted 06-01-2019 06:59 PM

Rich, re PC 73XX, I found it @ HD. My boxes are curvilinear in both vertical & horiz directions. I start w/ 1.25” to 1.375” thick wood and using a router bit and bandsaw, I cut the curves down to a min carcass wall of 1/2”. I like what I read about the PC but can’t tell it will be versatile enough to get into the curves of box. What do you think?

Re the source for Mohawk, I had been buying from Shellac.net which carried only the Behlen brand. But they now also carry Mohawk. Your source has a better price so I will buy from them next project.

Thanks for info,
Ron

View Rich's profile

Rich

4832 posts in 1071 days


#9 posted 06-01-2019 07:24 PM

No, I don’t think the PC would be suitable for tight curves. I only use it on flat surfaces.

-- There's no such thing as a careless electrician

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ronlatour

12 posts in 142 days


#10 posted 06-01-2019 07:36 PM

Rich, thanks for the tip anyway.

Ron

View UnmarkedBill's profile

UnmarkedBill

11 posts in 118 days


#11 posted 06-01-2019 08:33 PM

What works for me is 12” mops running about 850 rpm. Same idea as a slow speed grinder with big wheels.

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ronlatour

12 posts in 142 days


#12 posted 06-02-2019 03:03 PM

UnmarkedBill, thanks. I looked at my regular sources but didn’t immediately find what I think you mean. Can you provide me website?

Thanks,
Ron

View ronlatour's profile

ronlatour

12 posts in 142 days


#13 posted 06-02-2019 04:39 PM

Folks, here’s the result so far. Before I resprayed, I lightly rubbed the entire surface with gray synthetic wood with a little more pressure on and around the rubbed areas. I did manage to lighten up some of the stain. So, I did some touch up.

As of now, I applied 3 new coats of Minwax lacquer. Unfortunately, the rubbed areas are still visible as streaks between 1/2’” to 2” long and about 1/8” to ¼” wide & their color is a bit lighter than the surrounding walnut. I see 3 possible solutions & can’t decide which way to go for fear of making the situation worst.

1. Accept the defects, continue w/ 1 to 2 coats of lacquer and hope that they will become less obvious following the rub out stage. As the urn ages, the lighter areas may darken.

2. Feather sand (320grit) the defects to change their shape a little. Touch up the stain as necessary & start respraying again w/ Minwax. I expect that this won’t make the defects disappear but just be less conspicuous.

3. Start from scratch by sanding the entire surface down to bare wood & start over using a different lacquer such as has been recommended. I expect that this option will diminish the geometric appearance by rounding down decorative corner shapes created by the template & router bits.

Does anybody see other ways out of this mess. I’m learning more about lacquer than I ever wanted to learn.

Thanks,
Ron

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