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SW Conversion Varnish, 2K Poly over Shellac

Bob J Member

I have been using General Finish's High Performance Poly over Shellac on coffee tables etc and would like to use something more durable as far as scratch and moisture resistance and thinking about a 2k polyurethane (maybe Sherwin Williams T73V120) or Sherwood Williams Conversion Varnish -CCF24 (V84F81 bright rub). I work with mostly figured wood and use either BLO or Tung oil to enhance grain and use the shellac as a barrier coat as well as a sanding sealer. Does anyone know if the 2k poly or the conversion varnish can be used over shellac without adhesion issues, etc. and is either really more durable then the water borne GF poly.

10/26/15       #2: SW Conversion Varnish, 2K Poly over ...

try it and let us know how that works for you - may take a year or so;. or you can use sw's barrier coat - assuming they have one. and you can dye tint it to match the shellac you use

10/26/15       #3: SW Conversion Varnish, 2K Poly over ...
Leo G

I for one wouldn't be applying a catalyzed finish over shellac. I'd put it over a vinyl sealer.

I don't know about SW 2K, but recently I've been using MLC's Polarion 2K and it's very durable. I made the mistake of letting it cure for 3 days and then trying to sand it back hard (full fill on red oak) and it took 12 sheets of 5" 220 sandpaper to sand back a 25"x114" countertop. I got about 1 1/2 sq ft of sanding done before the paper wore out and would barely scratch the surface of the 2K. Then when we were installing it we had to scribe some large melamine cabinets to the wall and it required us to move the cabinets quite a few time around the counter. At the end we looked and not even a mar, let alone a scratch. But you have to let it cure at least 3 days before you get this resistance. On day one it actually scratches very easily, a paper bag will scratch it.

10/27/15       #4: SW Conversion Varnish, 2K Poly over ...
the google

leo - not to hijack the thread, but are you liking the full-finish (filled pores) look of the polarion? we shoot ilva 2k poly and i really like that it is a two coat system. we aim for an open-pore feel with our finish and i don't think this is possible with polarion. we were recently told by our mlc distributor about it and that it is a two sealer, two top coat system. this sucks for achieving an open-pore finish and for production times.

i'm curious as to your experiences.

to the op - yes, vinyl sealer/barrier coat is the way to go.

10/27/15       #5: SW Conversion Varnish, 2K Poly over ...
Leo G

Full fill certainly isn't a 2 and 2 finish. But I wasn't using a AAA pump at the time but an HVLP and had to thin it 20%.

Lots of sanding back hard with the sealer.

I could easily see using it thinned 5% out of a pump and doing a 1 and 1 coat. I did it on some shelves and they looked nice.

10/27/15       #6: SW Conversion Varnish, 2K Poly over ...
Bob J Member


1. Why wouldn't you apply a catalyzed finish over shellac?

2. Never used vinyl sealers, do they work as barrier coats?

I will check out the MLC Polarion, I do like their products.

10/27/15       #7: SW Conversion Varnish, 2K Poly over ...
Leo G

General rule of thumb is to never apply a harder finish over a softer finish. A catalyzed finish is a harder finish then shellac, so you shouldn't do it.

10/31/15       #8: SW Conversion Varnish, 2K Poly over ...
John Member

I really like GF's HP Poly for it's UV package, but their Enduro Clear Poly is much harder and far more chemically durable. Sprays just as easily as HP Poly, too.


10/31/15       #9: SW Conversion Varnish, 2K Poly over ...
Rick Mosher  Member


There are many finishers who use catalyzed finishes over shellac but I am not one of them. One reason is if the finish fails it is automatically YOUR FAULT. No debate there, you used the wrong product and are responsible for your decision. On small jobs that may be worth the risk to you, I was working on huge jobs and that was not an acceptable risk.

Most 2k urethanes are self sealing and will probably work fine over a fully cured oil. I never like used oil under a surface finish. I really didn't see a huge difference in the look and on highly figured wood like tiger maple or anigre I used a clear stain base concentrate that was compatible with my finish, dried much faster and gave me almost the same look as the oil.

Sherwin Williams used to make an oily wood vinyl sealer that would probably work for you if they still have it.

11/1/15       #10: SW Conversion Varnish, 2K Poly over ...
Bob J Member

I have used GF's Enduro Var clear poly for some applications but I really don't like it. It has no UV inhibitor, is not really clear as it leaves a slight yellow color like varnish and ,unless I am doing something wrong, it does not spray as nice a finish as the HP. I do like the HP poly but I usually build 7 coats before sanding & buff back and can only do 2 coats a day. The reason for considering SW's conversion varnish is that I was looking for something more durable and also I can put on 3 or 4 coats in one day and be done, and the finish does not need to be sanded back or buffed out.

The clear stain base concentrate sounds interesting, have never used or heard of it. What one do you use and how do you use it? Any recommendations?

SW has (S64T70, S64T72 and SB Concentrate Base S64T78) which are clear wiping stain bases specifically formulated to work with the their Stain Colorants. S64T70 is a low solids clear stain base. S64T72 is a low solids clear stain base developed for areas requiring a lower VOC stain offering. S64T78 is a high solids clear stain base designed for making custom stain bases.

I picked up some SW's vinyl sealer T67F6 which is a catalyzed vinyl modified nitrocellulose sanding sealer. According to the SW rep it will probably work as a barrier coat. He said to test it by applying the sealer then the top coat. When dry take a razor blade and score the finish in a hash tag pattern and put some scotch tape over it and pull it off, if any adhesion issues it will show up.

11/1/15       #11: SW Conversion Varnish, 2K Poly over ...
Rick Mosher  Member


I believe I used the high solids SW clear stain base concentrate. I tried wet sanding it in like an oil finish but just wiping it on and off wet worked fine for me. Try it out and let us know what you think.

11/1/15       #12: SW Conversion Varnish, 2K Poly over ...
John Member

Bob, I didn't say EnduroVar, I said Enduro Clear Poly. Completely different animal. Sprays just as well as HP Poly (I agree with your comment that EnduroVar doesn't spray as well) and is just as clear. It is much more abrasion resistant and much higher chemical durability. I can easily spray 4 coats a day. Never found need for more.


11/8/15       #13: SW Conversion Varnish, 2K Poly over ...
Bob J Member

I tested BLO and Sherwin Williams high solids clear stain base concentrate to pop the grain on some Curly Maple. The clear stain base concentrate was wiped on and off wet and the BLO was applied over 10 minutes for absorption. When wet I did not see any difference in the figure pop. I let that dry one day and did not see any difference in the figure pop, in fact I think the clear stain popped the figure slightly more. I then applied SW's Vinyl Sealer catalyzed and two coats of SW's Conversion Varnish to both samples. The figure pop was as good if not better on the clear stain sample over the BLO sample.

I did do an adhesion test when dry on both samples by taking a razor blade and scored the finish in a hash tag pattern and put some scotch tape over it and pulled it off, did not see any adhesion issues.

I am going to go with the conversion varnish for some projects. The two draw backs for me are the toxic issue and the smell, so time will tell. I will try GF's Enduro Clear Poly when I get time to see how I like that.

2/7/17       #14: SW Conversion Varnish, 2K Poly over ...

We do tons of cabinet refinishing, and use Ilya 2k poly, catalyze at 10% exclusively. We prime both new, and refinished cabinets with Bin, which is white pigmented shellac. Have been doing this for years with 0 failures. We probably do around 30-40 jobs per year employing this process.

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