Water Rings in EM6000

[David Huston]

Made some walnut placemats for a customer and 1 week after she picked them up she was calling about rings left from cups. Finishng schedule was:
2 thin coats BLO each side
Sealcoat 50:50 with DNA
4-5 coats Target EM 6000 semigloss

I told her that the white rings should go away but I know that isn't a fix. I was wondering about water Rings with water borne lacquer but I couldn't find any answers online specific for water borne so I went ahead with it. Probably going to cost me! Would respraying the items with Target conversion varnish or polycarbonate solve the ring issue or do I need to try something different. I like the water borne since I can spray it but not against going another route to fix this problem. Any help is appreciated.

[Wayne Lomman]

David, the catch was this: "nitrocellulose-type appearance and performance" (quoted from the manufacturers spiel). You will need to rework using something more durable. Use 2K polyurethane. It is 100% reliable for this. You can get it at any half serious paint distributor but not your big box retailers. I have to ask, why the oil at the start? If it was colour you were after, use a compatible stain then straight on to the clear coat. Cheers

[Patrick Chase]

IIRC EM 6000 is robust to room temperature water, but has the issue you describe at elevated temperature.

For future reference, there is a red flag for this in Target's literature but it isn't as obvious as one might like. The KCMA result for water in the EM6000 datasheet is explicitly qualified as "room temperature". Their more durable varnishes like EM2000 and EM8000 are both specified as passing the more common "warm water" (100F) test condition.

That brings me to my last point: Wayne is right that 2K poly is the bombproof solution here, but you can do better than EM6000 even with a water-based finish. EM6000 is really optimized for lacquer-like appearance and "burn in", and that optimization come with reduced durability and chemical resistance. The fact that the finish "burns in" means that the dried finish must dissolve in its own thinner, like shellac and nitro.

Finally you could try Target's CL100 cross-linker, which is billed as improving chemical resistance by improving inter-resin-glob bonding. When I asked about it here a while back it seemed not to be widely used, though.

[Jim Becker]

EM6000 isn't the best Target product to use for this kind of project for the reasons that Patrick mentions. I really do thing that the temperature of the liquid had bearing here, too. They have several more durable coatings to consider. In my experience, they all spray similarly to the EM6000, so application shouldn't change much, if at all. A two part polyurethane would certainly stand up, but as far as I know, it also requires a bit more finishing infrastructure than most folks have in the home or small business shops for safety, etc.

[John Kee]

Forget the antiquated BLO and tint the Sealcoat or just tint the topcoat. The topcoat you're using is way to thick, stick to at most 3 topcoats especially if using Sealcoat. Did you let the final product cure at least 14 days before giving it to the customer. If you have to redo use EM2000 it has much higher water resistance because of the ability to both interior and exterior. Also educate your customer to cleanup spills. As a last resort consider 2K poly.

[John TenEyck]

I've never had that kind of trouble with GF's EnduroVar, and there are even better waterbornes, so don't discount all of them. There even is a waterborne 2K Poly. I found one by Chemcraft, but haven't actually used it yet. It's Aqualux Post-Cat WB Clear Topcoat, 423-73XX. You might want to look into that as an alternative to solvent based products if you are in a shop w/o appropriate environmental controls, like me.

John

[Patrick Chase]

I've never had that kind of trouble with GF's EnduroVar, and there are even better waterbornes, so don't discount all of them. There even is a waterborne 2K Poly. I found one by Chemcraft, but haven't actually used it yet. It's Aqualux Post-Cat WB Clear Topcoat, 423-73XX. You might want to look into that as an alternative to solvent based products if you are in a shop w/o appropriate environmental controls, like me.

John

IIRC GF Enduro lacquer (their counterpart to EM6000) does have similar limitations, but your broader point is spot on, and basically the same one Jim and I were making: Other water-based finishes from both Target and other suppliers are much better in this regard.

I wouldn't use nitro lacquer for a placemat either, FWIW.

Have you tried General's post-cat water-based conversion varnish? I'm tempted to order a gallon just to see how much performance gain there is, but as you point out the top-end 1K varnishes like EnduroVar are sufficient for most needs.

[Patrick Chase]

One additional thought: I think that there's some confusion in this and some other recent threads about how modern water-based coatings work. In particular there seems to be a widespread assumption that all water-based coatings are coalescing finishes like latexes. Flexner's book in particular is a significant culprit in this regard, as his knowledge was dated when he wrote it and has only become more so since.

One big change that has happened in the last decade or so is the advent of water-based oil-modified urethane finishes. These are water-based finishes that contain oil-linked urethane resins just like solvent varnishes, and that cure by cross-linking again just like solvent varnishes. This article from 2000 provides some context. The online version is missing the figures, but the text gives a reasonable sense for the state of the art at that time, which was already pretty good.

The key thing to note here is that water-white finishes like EM6000 and the corresponding GF lacquer are generally NOT oil-modified urethanes (due to yellowing concerns), and that limits their durability. State of the art water-based varnishes like GF EnduroVar and EM8000 are in a different league than either those lacquers, what some posters seem to be assuming about all water-based finishes, or what Flexner describes in his book. I believe that EM2000 is an oil-modified alkyd and in a similar class.

PS - Water-based oil-modified urethanes *are* true urethanes, so the old saw about "all waterbased finishes being acrylics" is also obsolete.

[John TenEyck]

IIRC GF Enduro lacquer (their counterpart to EM6000) does have similar limitations, but your broader point is spot on, and basically the same one Jim and I were making: Other water-based finishes from both Target and other suppliers are much better in this regard.

I wouldn't use nitro lacquer for a placemat either, FWIW.

Have you tried General's post-cat water-based conversion varnish? I'm tempted to order a gallon just to see how much performance gain there is, but as you point out the top-end 1K varnishes like EnduroVar are sufficient for most needs.

No, Patrick, I haven't tried the Enduro Conversion Varnish yet. I've been scared off by the problems several people have reported about adding the catalyst and pot life. I'm looking into the Chemcraft WB 2K product to see if I can get it. I don't do many tables but that's where I would use it. I have to thank Wayne and his oft repeated advise to just use a 2K poly and all your problems will go away for finally focusing my attention on them.

FWIW, I just did some testing on Enduro Clear Poly and Lenmar Duralaq against Windex and Fantastic, both ammonia containing products. The Duralaq was damaged badly in only a few minutes, while nothing happened to the Clear Poly even after an hour. I seem to remember that Clear Poly doesn't do as well against acetone as EnduroVar (full recovery), but don't quote me on it. But I think that's what drove me to choose EnduroVar when I need max. durability in my world of WB spray products and Clear Poly for nearly everything else. I have yet to try EM-2000 or EM-8000 but am looking for an opportunity. I also have a gallon of EM-6000 to try but haven't had an appropriate project yet. My only experience with TC's products so far was EM-9300 and it was a disaster with bubbles so I'm a little gun shy of their products. FWIW, the Duralaq sprayed beautifully and I would use it again where chemical durability is not needed.

John

[David Huston]

Thank you all so much for the input. I have not heard back the customer yet to see if the rings went away. I have some em9300 that I was going to spray over the em6000. I left a message for Jeff Weiss to ask if the 9300 would be more resistant to water Rings but haven't heard back from him yet. I have used it on a computer desk top before and didn't have trouble with bubbles. I can say that it does yellow a little bit as the computer top was white and you can definitely see a color change. Fortunately it is my desk! I have used the Enduro clear poly before and it was great. I just had this em6000 left over and thought that it would be ok for these placemats. Live and learn! I had some em8000 but it was a bit past it's date and had turned a little pink so I threw it out. Might just have to order some more of that if it is the best option. Thanks again!