Bubbles in my Finish?

This week’s question comes from Zac who asks; “I am sealing a door I stained and I keep getting these little bitty air bubbles. I can sand them off, but they keep coming back. What do I do?”

brushAnd my response was: “Hey Zac. Bubbles can come from a few different sources. One can be the wood itself. The pores and pockets on the surface of open pored woods like oak and ash can sometimes trap air, which wants to bubble out after you coat it with finish. You can also introduce air into the finish if there is a lot of air in your brush (if you are brushing). Letting the brush soak in your solvent for a while before using it and being careful not to agitate the brush too much will help quite a bit. Bad brushing technique will also lead to bubbles. So depending on what you are using and how you are using it, the culprit could be a number of things. One of the best ways I know to prevent bubbles is to wipe the finish on with a rag instead of using a brush. You will need to dilute the finish about 50% with mineral spirits or naptha, and as a result, you’ll have to apply more coats. But its well worth it for the smooth finish you’ll get in return. Good luck!

Category: Finishing

Comments

  1. Neal February 23, 2009

    What kind of rag would you recommend to avoid problems with lint and dust?

    Thanks!

  2. Marty February 23, 2009

    If you have to brush on the finish, use a foam brush and make sure it’s saturated in the finish. Wiping on the finish is the only way to go though. Use old t-shirts or you can buy torn up t-shirt material at Lowe’s for about $5.00 for a bag of 12. You can cut these up into smaller pieces for wiping.

  3. Greg February 23, 2009

    I have worked with fiberglass gelcoat in the past and found that brushing back and forth using both sides of the bush created bubbles in the finish. We only used one side of brush and apply all in same direction if you can. Now I practice this technique whenever I apply a finish to all my woodwork.

  4. Dan February 24, 2009

    One thing else to mention – the finish should be gently stirred, not shaken. Shaking will introduce air bubbles.

  5. JHop June 3, 2009

    Has anybody used microfiber cloths to wipe on stain? I have one that doesn’t work too well on windows (which is what the product was advertised to do….) that I’m trying to find other uses for.

  6. When putting down some finishes that tend to have bubbles show up you can use a drinking straw and blow on the bubbles. The CO2 will help the finish to release the bubble. this does not work with all finishes but does with some.

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