Finish to turn table top into giant coaster?

[Grant Trotter]

Hello! This is my first post here. I've searched for an answer to this question before creating an account, so please forgive me if I've overlooked it. I saw similar questions but not quite what I'm looking for.

I'm researching making a coffee table for a client who wants a very water-resistant surface. They want to make coasters obsolete. I don't want to say, "Try to avoid putting cold drinks directly on the table, but if it happens occasionally, it should be fine." I want to say, "Put your cold drinks right on there and leave them for a few days. Spill them a little while you're at it. It will definitely be fine."

I'm open to using high-end products if they perform better.

Here are some of the options I've found in my research thus far (some from posts on this forum), listed in ascending order of how appropriate they seem based on what I've learned:
- Waterlox Original or Waterlox Urethane
- General Finishes Arm-R-Seal
- A skim coat of epoxy (what I have on hand is West Systems)
- General Finishes Conversion Varnish

A few notes:
- It will be a 46'' wide black walnut glue-up which can be expected to move seasonally about 6.5% (0.3in), so whatever I use needs to accommodate that without cracking or buckling.
- A satin sheen is preferable.
- I'd prefer thin film finish over a thick bartop type finish if possible.

Basically I want the finish to pass this test, but I don't want to spend hundreds of dollars on all the different finishes to administer the test myself: Apply the finish on some black walnut, put a cup of ice water on it, let it condensate heavily and leave it there for a few days, remove the cup and wipe off the water. If the finish looks good as new immediately after and long after, then it passes the test

Thanks so much for reading all this! Any input is much appreciated!

[Bennett Ostroff]

Any oil-based varnish - Waterlox, Arm-R-Seal, Minwax polyurethane/wipe-on poly, etc. - will accomplish this. As long as it's applied properly and allowed to cure. All those finishes come in satin sheen. All of these will accommodate seasonal movement. My plug would be for the Minwax because it seems to be easiest to apply.

I'm not sure I would tell them they can leave liquid on there for days. Maybe just tell them it's a highly liquid resistant finish, but cleaning up spills in a reasonable amount of time will help preserve the finish long term.

[Peter Rawlings]

I'd go with a catalyzed finish...fast to cure and wear resistant. I've shot lots of ML Campbell Krystal conversion varnish and it's really tough, although I've never tried a test like you're suggesting. If you're willing to wait for results, I'd make a sample just to satisfy my own curiosity. They have another product, Polarion, which is catalyzed polyurethane. Supposed to be even tougher, although I've not used it.

To be honest, I don't have much experience with General Finishes, so can't be helpful there.

[John TenEyck]

Epoxy without added UV protection is not a good choice as it will yellow over time. However, an epoxy sealer is a very good first step. The most durable topcoat I know of is a 2 component urethane; think automotive clearcoat, and that is the direction I would pursue. Waterlox, ARS, etc. are all excellent products but I don't think they will survive days of water exposure with zero damage.

John

[Tom M King]

Moisture Cure Urethane floor finish. Probably not available in California, as it has every solvent on the dangerous list in it.

[andy bessette]

On yachts an extremely durable finish is created by first applying many coats of WEST epoxy (see Gougeon Brothers specific instructions for this), which is block-sanded back down before applying a final finish of polyurethane varnish or clear linear polyurethane. The finish coats should contain high UV inhibitors if long exposure to sunlight is expected.

[Edward Dyas]

Hello! This is my first post here. I've searched for an answer to this question before creating an account, so please forgive me if I've overlooked it. I saw similar questions but not quite what I'm looking for.

I'm researching making a coffee table for a client who wants a very water-resistant surface. They want to make coasters obsolete. I don't want to say, "Try to avoid putting cold drinks directly on the table, but if it happens occasionally, it should be fine." I want to say, "Put your cold drinks right on there and leave them for a few days. Spill them a little while you're at it. It will definitely be fine."

I'm open to using high-end products if they perform better.

Here are some of the options I've found in my research thus far (some from posts on this forum), listed in ascending order of how appropriate they seem based on what I've learned:
- Waterlox Original or Waterlox Urethane
- General Finishes Arm-R-Seal
- A skim coat of epoxy (what I have on hand is West Systems)
- General Finishes Conversion Varnish

A few notes:
- It will be a 46'' wide black walnut glue-up which can be expected to move seasonally about 6.5% (0.3in), so whatever I use needs to accommodate that without cracking or buckling.
- A satin sheen is preferable.
- I'd prefer thin film finish over a thick bartop type finish if possible.

Basically I want the finish to pass this test, but I don't want to spend hundreds of dollars on all the different finishes to administer the test myself: Apply the finish on some black walnut, put a cup of ice water on it, let it condensate heavily and leave it there for a few days, remove the cup and wipe off the water. If the finish looks good as new immediately after and long after, then it passes the test

Thanks so much for reading all this! Any input is much appreciated!

If the wood isn't light in color you could just use an oil based polyurethane. It would be waterproof but would yellow as it ages. This would look bad on light wood. The conversion varnish would be a good choice. It would make a harder finish than polyurethane.

[Edwin Santos]

I would try a sample piece finished with waterlox marine or Epifanes clear and see if it passes the test. With both of these finishes it is important to thin the first coat substantially so it penetrates into the wood. The successive coats are thinned progressively less and will sit on top thus building up the finish and protection. Waterlox sells a separate product called marine sealer which is intended to perform the function of the penetrating first coat. Another reason I like these spar varnishes is that they are designed to flex to accommodate wood movement, which is one of your concerns also. These products are used on boats and outdoor furniture that gets rained on, so I think they should stand up to the task.

If it were me, I would get a pint of Epifanes and do the test for the $20 or $30 it will cost.

Just remember a high protection finish like we're discussing will be a very built up look, some might say plastic looking. Think of what a wood bar finish in a pub looks like. And of course a pub is after the same kind of protection your client is seeking.

[Tom Bender]

I know your question is about top coating and you now have some good answers. I'd like to throw in a caution about walnut. Light, especially sunlight is going to make it fade. Objects on it will leave shadows. Start with stain. Use a topcoat with UV blockers.

[Steve Schoene]

A sheet of tempered glass will be sure to work as required. Asking finishes available outside of industrial facilities to work is questionable and likely to require regular refurbishment.

What’s wrong with coasters?

[Carl Beckett]

I agree with the glass approach.

Then marine/spar varnish.

I have not had good luck with epoxy (used it on an exterior door and it did not turn out well, nor hold up well). I am sure something was done 'wrong', but to this day I do not know what. I may give it another try someday but am just saying to run a test piece before committing to it.

[Steve Schoene]

Carl. The problem you had is mostly with epoxy. It is not very uv resistant for exterior doors. It can work outdoors if covered by multiple coats of marine grade spar varnish such as Epifanes. I’ve never found that it levels really well either so it needs meticulous application for a good look.

[Carl Beckett]

Carl. The problem you had is mostly with epoxy. It is not very uv resistant for exterior doors. It can work outdoors if covered by multiple coats of marine grade spar varnish such as Epifanes. I’ve never found that it levels really well either so it needs meticulous application for a good look.

I think a number of problems. First, perhaps it was not thinned enough so as you say did not penetrate sufficiently, then did not level. But the bigger problem was movement (maybe). At all the seams (a nice rail and style panel door) hairline cracks developed and in this particular environment (my neighbor) mold got in. The mold around my house is super aggressive and gets into everything.

My neighbor tried to rework it a bit, which didnt really work well either. Could live with the poor leveling, but it didnt provide the protective barrier it was supposed to.

[andy bessette]

...it was not thinned enough...

Generally you don't thin epoxy. And it is never a good idea to add anything to it that is not specifically recommended by the formulator.

[Carl Beckett]

Generally you don't thin epoxy. And it is never a good idea to add anything to it that is not specifically recommended by the formulator.

I misread an earlier post then. We used it right out of the can (I just thought someone suggested thinning)

Before doing the project, I read many posts here on different options for external doors and went with the epoxy based on the success of others. It was not cheap ($200 for this one project). And it did not work well.

My neighbor thanked me for the efforts (was quite a difficult project because it also meant hand fitting a door into an antique jamb). Which we got to come out pretty well, just wish the finish held up better.