Mulling Smalt PIgment and Crystal Glass Medium

 Blue Morpho  10"x8"  oil/panel by Sarah Siltala

I was reminded recently of a couple failed attempts in the studio, one: to make a medium with powdered crystal glass and two: make Smalt into paint.  In my previous experiments I had used linseed oil alone without any other additions to the mixtures.  This was a mistake, both Smalt and crystal glass are heavy particles that do not mix easily with oil.  They need an additional stabilizer to create a smooth consistency that will not separate.  I thought about my experience with both and suddenly a light bulb went off, I immediately pulled out my unusable tube of glass medium and ordered another batch of powered smalt pigment.

While I waited for the smalt to arrive in the mail I went to work on my tube of hardened glass medium. It had separated in the tube and I had to cut it open to scrape out the hardened mass of glass and re-mull it.  Below you can see the hardened chunk of medium and the oily residue.  It needed some sort of stabilizer but I did not want to use wax, and I did  not want to use alumina stearate-a paint stabilizer and cheap filler found in modern manufactured paints. 

I re-mulled the leftover glass chunk with my handmade linseed oil, below you can see the result, a nice smooth mixture.  

I divided the linseed/glass mix into two jars afterward.  To one of the jars I added fumed silica.  I've experimented with making my own medium with fumed silica before and thought if I added this as a stabilizer maybe my mixture would not separate like it did before.  Below on the left is the glass/linseed oil mix and on the right I am adding powdered fumed silica.  I have a post about my previous mixture with linseed oil and fumed silica HERE.  When fumed silica is mixed with linseed oil to make a medium it creates a lovely clear gel and is fantastic to add to oil paint.  It thickens up quite a bit and I'm hoping to have the same effect with my crystal glass mixture.

I also fill a third jar with linseed oil and fumed silica, to prepare for my later experiment...

 Here are my three mixes:

And, 24 hours later:  The linseed/glass mix is already settling and the oil rising to the top, the mixture with linseed and fumed silica is consistent and has not separated.  The fumed silica addition created a stable mixture.  I go ahead and tube it and label it. 

You have probably guessed by now that I intend to mix Smalt pigment with linseed and fumed silica.  Smalt is incredibly difficult pigment to make into usable oil paint.  I've read that adding wax can help as a stabilizer, but when I asked the director of Natural Pigments about using the pigment in oil he recommended mulling and using it the same day.  In my first attempt to make paint with just oil and powdered pigment I found it to by totally unpredictable and when I let it sit for 24 hours to 'sweat' it had solidified completely and had to be re-mulled.  It never really became a stable consistency I could use for paint.

Smalt is a historical pigment and a beautiful, delicate shade of blue.  Very unusual.  It's incredibly transparent and has been known to fade or turn green over time.  Luckily potassium has been found to combat the discoloration and fading and Natural Pigments brand of Smalt contains plenty of potassium so no worries there.  Mixing with lead white will also help against future fading, but Smalt has such a low tinting strength I prefer to use it as a glaze.

I add the smallest amount of oil I can to create a thick chalky paste, this will thin out to an ink like consistency immediately.  I don't have to work hard at all to mull it and it's best not to over-mull this pigment anyway.

 

I'm surprised at how thin the oil becomes, but now I add my previously prepared mixture of oil and fumed silica which has become a thick gel.  After a quick mix together with the ink like Smalt I have an actual paint like consistency!

 The paint has become buttery and smooth:

 Here are my tubed up experiments, both with the addition of fumed silica as a stabilizer:

Below you can see them again, almost two weeks later.  I wanted to wait before posting to make sure the tubes wouldn't seize up and pigment and oil separate again over time.  So far both the Smalt and the crystal glass medium have remained consistent in the tube and I'm really enjoying using them in my current painting.  So far so good!