Those Pesky Bubbles

It's quite easy to generate air bubbles in your acrylic materials.  As we aggitate our acrylics, pockets of air will get trapped in our paint layers and depending on the viscosity (thickness) of the material, these bubbles may show up while the material is still wet or may rise to the surface during the drying process, to be discovered only after the acrylic film is dry. 

In my paintings I use a rubbing technique with my color...I build up texture with smooth gels or pastes, then buff color over the texture with a cloth.  As I'm doing this, some of my color will get pushed down into little craters I didn't even know were there, and most of the time they are unwanted.  The craters are formed by air bubbles that rise to the paint surface and pop while the paint is drying.  With thicker mediums like Molding Paste, and gels such as Regular, Heavy, Extra Heavy and High Solid Gel (any sheen), you may not know that the bubbles have formed especially if you applied them thick, because the air bubbles will have to travel out of the lowest part of the gel layer.  As you lay down texture with your brush or palette knife, you may fold the gel/paste in on itself and trap air inside the gel layer.  This is similar to throwing and needing clay...as you fold the clay over it traps air, so you throw it onto your table and knead it with your hands to work out those air bubbles.  We cannot treat the acrylic layer with our hands the way we would clay, but we can be mindful of how we are treating our wet materials to avoid those pesky craters.

One of the best gels in which to see these bubbles form is Clear Tar Gel, especially when you are trying to get an even layer while moving it around with a palette knife.  Now, on this sample board I over-aggitated the gel so you can see how dramatic these bubbles can get.  In your own practice, under mild aggitation, it is not likely that this many bubbles would form...

Clear Tar Gel layered over an underpainting, the gel is still wet and immediately you can see the air bubbles on the surface.

If you let these bubbles dry like they are, they will pop on the surface leaving a pock-marked, cratered surface finish

Here I applied some Van Dyke Brown Fluid Acrylic with a damp rag over the surface so you can see how your color can get pushed into the craters

Some of you may enjoy this cratered look, but if you want to avoid it here are some tips:

For thicker materials, apply them with lighter pressure and from an angle coming in from the side, in my experience this will push any existing air bubbles closer to the edge of my painting surface, so if they don't disappear entirely, they are not as obvious right underneath the main portion of my painting.  Up and down motions with a palette knife to texture a gel surface are going to push more air into your gel.  I like to imagine I'm icing a cake while applying gel, think about applying your marks gingerly.  If you like to go crazy when making textured marks into your smooth gels and pastes, just be mindful that air bubble craters may be unavoidable.

Absorbant materials like Light Molding Paste, Fiber Paste, and Crackle Paste will dry with more porosity, so I have never had an issue with bubble craters in these materials.

For lower viscosity materials like Clear Tar Gel, Self Leveling Gel, Polymer Medium, Fluid Acrylics, etc... you will see the air bubbles right away and can treat them on the surface by spritzing some rubbing alcohol from an atomizer bottle.  The atomizer bottle (vs. a bottle with a more direct spray) will give you a fine mist that will pop all surface bubbles.  Sometimes you have to do more than one spray to eliminate all visible bubbles.

Clear Tar Gel before rubbing alcohol...

Clear Tar Gel after rubbing alcohol...notice the top portion of the gel layer and how the bubbles have popped. 

In the case of Clear Tar Gel, it will level, so those popped wet craters (from larger bubbles) will flatten out as the paint dries.