Thinning waterborne polyurethane

[Prashun Patel]

I have 2 kids arts and crafts tables that take a beating from my kids' stray markers, glue, and pencils. Both are painted and need to be refinished (paint, per LOML).

I'm planning to use Benjamin Moore's Aura semigloss, and then a waterborne poly on top of this.

Is this a good plan? If yes, then I'd like to spray the poly on. Should I thin it? With what?

[Jamie Buxton]

You can thin waterbornes with water.

My sprayer came with a viscosity-measuring cup, and a spec for optimum viscosity for this particular system. If you don't have that, you can determine it experimentally. You spray some, observe the results, thin some, spray that, observe the results, etc. You record how much thinning you do, and when you get a result you like on your tests, you do more of that to your furniture.

[Prashun Patel]

Great. Thanks.

[Matthew Voss]

Why not just use this?:

http://www.targetcoatings.com/oxford-super-clear.html

[Steve Schoene]

Not really. There is usually a very narrow range in which you can add water, typically no more than about 10%, occasionally a shade more, depending on the particular product and the manufacturer's recommendations. Thin too much, and the water takes too long to evaporate and the little packets (latexes) of finish don't coalesce properly, or link together very strongly.

You are much better off choosing a finish, such as Target USL, that is manufactured at a spraying viscosity.

[Jim Becker]

There is little point in top coating the Aura....it's incredibly durable and completely washable, including in flat sheen version. It develops a very hard surface once fully cured and has silca in it's formula. Our entire addition and great room were painted with the Aura flat and I can personally attest to the durability and washability of the product.

[Jamie Buxton]

... It develops a very hard surface once fully cured....

How long, in your experience, does it take to fully cure? It is a latex paint, and those have a bad rep for taking a very long time to fully cure -- y'know, to the point that you can fill a bookcase painted with the stuff.

[Prashun Patel]

It's latex modifed with some kind of 'hybrid' resin, which I believe means acrylic and urethane or alkyd resins.

I used InslX Cabinet Coat for closet shelves before. Cures hard and 'blockless' pretty quickly, so I imagine the Aura does too.

However, one of my kids' tables is done in Cabinet Coat. While these kinds of washable paints are good for occasional spills, they're not (IMHO) intended for the beating an arts and crafts table takes. That's why I was considering a poly topcoat.

If this doesn't work well, I'll just go to replaceable top skin sheets of 1/8" hardboard.

[Joe Chritz]

Since you can spray I highly recommend you look at the Target coatings line of finishes. Specifically the Oxford super clear 9000 polyurethane. I haven't used that product but their other stuff is top notch.

The 9000 is water clear and formulated for table tops and the like, specifically for top coating painted surfaces. Thinning it with water allows it to be wiped on if desired.

Normally I would use their conversion varnish for a table top but since it is top coating paint you don't want anything that has an amber tone to it.

Since you are using the top coat for durability I would get a tinted USL from them also and use that for color coat. A call to their tech (who I have always had answered by the president) or a visit to the finishing forum their will answer any questions.

Seems like a waste to buy the best paint available and top coat it with something else, hence my unsolicited opinion at alternate options.

Joe

[Prashun Patel]

Your opinion is entirely solicited! Thank you! I may go that route.

[Jim Becker]

How long, in your experience, does it take to fully cure? It is a latex paint, and those have a bad rep for taking a very long time to fully cure -- y'know, to the point that you can fill a bookcase painted with the stuff.

I don't recommend any latex product for a bookcase because blocking (the sticking) doesn't go away with a cure. I was only commenting on durability relative to the Aura product.