How to apply polyurethane over a stain?

Question

I am going to apply a clear matte polyurethane (oil based) on top of a mahogany stain, (also oil based)

I'm considering using a clean rag as opposed to a brush to avoid bubbling and brush marks etc.

I don't really want to thin down the poly before applying but wanted to get some advice first on why thinning might be the best and also to what ratio.

Thank you.

Innov8tive · Answer

Hello @MitchellMc

I'm going to.read the back of the can. The reason I mentioned using a rag was just considering using another applicator rather than a brush but will think about it.

Also I did a test on scrap wood and there were fine bubbles but if it happens again I will give that a very very light sand with 240 grit before applying another coat.

Good advice. Thank you.

MitchellMc · Answer

Hi @Innov8tive,

I'd follow the application instructions provided by the manufacturer of the polyurethane you're using. Applying it with a rag or thinning the product should only be done if the manufacturer specifically recommends those methods.

For instance, Cabot's 1L Matt Oil Based Cabothane Clear Polyurethane Timber Varnish can be applied with a brush or spray gun, and the manufacturer does not recommend thinning it for brush application.

Most standard oil-based polyurethanes are formulated to be applied at their supplied consistency using the recommended applicator. Thinning unnecessarily can affect the film build, drying and ultimately the performance of the coating.

If you let us know the specific polyurethane you're using, I'd be happy to check the recommended application method for you. Though if rag application and thinning provided the best results, it would be something they would instruct on the can.

Let me mention @jess56, @SaraK, @kendallmac, @TaylerMayd and @Elljames to see if they have any thoughts.

Please let me know if you have any questions.

Mitchell