Tone's Notes

The following tips are from a FAQ found here:

One of the most common and vexing problems with water-based products are the air bubbles, or air entrapment. Any fast-drying product tends to have problems with air bubbles, but air bubbles are more inherent to water-based products because of the way they interact with the pores of the wood, literally forcing air/gas to escape. Allowing or causing the finish to dry too fast or allowing air movement during the initial drying process is the most common cause of air bubbles--the finish just does not have enough time to flow and level before it sets up. The following are a few time-honored “air bubble” remedies that I have compiled from my experiences and others..

1. Prevent drafts or moving air during wet film setup, at least until the finish has leveled out. In the case of water-based finishes, give it an hour and then ventilate the work area.
2. Control your Air temp & Humidity. Follow the manufacturer's recommendations.
3. Experiment with different film thicknesses.
4. Do not sand with stearated sand paper and make sure the surface is properly prepared.
5. Experiment with your spray gun settings.
6. Don't use HVLP turbine type spraying units, as they tend to warm the air and cause the finish to dry too quickly. Use HVLP conversion guns, or conventional sprayers
7. Depending on the product, thin the finish with water--start at 10% and add more if needed. Some products suggest you use their retarder. Best to follow manufacturer recommendations.
8. Lightly dampen the surface, with a sponge or a water bottle sprayer. The water will travel through the film keeping it wet longer, so the bubbles have more time to break.
9. If you are brushing, do not use a sponge or foam brushes, do not shake the finish, and properly prepare the surface. If the grain raises, it will cause a rough surface that will cause air bubbles as you pass your brush over the rough surface.

From Steve Mickley:

“Stearated sandpaper contains something called Zinc Stearates in its coating to make sanding easier by preventing "clogging". Zinc Stearate is a soap like material that is also used in many "sanding sealers" for much the same purpose - a benefit of dubious value given the alternatives available and the potential downside. The problem is that it is quite soft, not at all moisture resistant, and can cause adhesion problems in incompatible finishes. As a result, whether in the form of sanding sealer left behind under your topcoat, or in the form of a film left on the surface after sanding, this stuff can cause problems. While there are many who would argue this point, I feel about Stearates in the shop much the same as I do about silicones; I don't want them anywhere in the building.”