I use a large spoon with which to mix the primer. When I paint the primer onto the mat board, I use a foam roller rather than a paint brush. This is mostly because if I want to use pencils on it, the paint brush does not produce as even a surface as a foam roller will. These are the foam rollers I use:
First thing I do is to paint a light layer of HP gesso or Liquitex matte medium on the back of the mat board, being sure not to use too much. After the back of the board has thoroughly dried, I turn it over and mark off the part of it I want to paint the primer onto. I make various sizes, the most common being 11" x 14" and 12" x 16". To mark it off, I use blue painter's tape. I then proceed to paint the primer onto the surface, being careful not to paint beyond the blue tape (although I am not always successful). However, if I go beyond the tape, it's okay because that part will end up behind a mat anyway.
I have learned to apply the primer in thin layers or the primer will not come out with an even texture usable for pencils. It is very difficult to get an even surface on the primer if you apply it in layers that are too heavy. Make sure you let the layers dry completely before adding another layer. Generally I use only two layers. If I apply much more than that it may end up saturating the board.
After the primer dries completely, I gently peel off the tape and place the boards into resealable plastic bags. Then I set very large, heavy books on top of the boards and leave them there for several hours. This simply makes sure the board lies flat.
Here are the results:
The first mix I made came out so-so. I used 1 cup gesso, 6 tsp. pumice powder, and acrylic color. It ended up being very coarse. I tested it and found it worked fine for soft pastels, but would not be appropriate for colored pencils. I did sand down the primer a bit, but it is still quite coarse. I call this color sandy beige.
The second mixture I made was much better! I mixed 1 cup gesso, 1 tsp pumice powder, and acrylic color. It came out much finer in texture. Although I haven't tested it yet because I just mixed it this afternoon and it needs to set for a bit. I call this color sky blue.
And finally, I mixed a medium coarse primer. I mixed 1 cup gesso, 2 tsp. pumice powder, and acrylic color. This also seemed to come out well, though, again I haven't been able to test it since I just made it. I call this color Raw Sienna.
CAUTION: When handling Pumice Powder you MUST wear a NIOSH approved nuisance dust respirator mask that will not allow the fine pumice powder to be inhaled. Pumice powder is made from volcanic ash and is a cancer agent if inhaled and will cause lung damage. It is also recommended that you use the pumice in an exhausting hood or glove box. Be sure to wear gloves when handling the pumice. In addition, I have nearby a set of goggles to wear.
When mixing the pumice into the gesso, gently fold it in so as to avoid creating any dust that might become airborne. Clean up your work area thoroughly after using the pumice. Do not use near food, cups, utensils, etc. I keep any utensils I use for mixing separate from my other utensils and only use them for mixing primer, nothing else.
I hope this article has been of interest to some of you. If you have any questions, please feel free to ask.
