Tuesday, January 29, 2013

106: Best chalk for painting

ONE OF THE primary ingredients for thick paint is chalk, otherwise known as Calcium Carbonate. The thicker I paint the more chalk I use. So it is important to have a good source of inexpensive chalk. I recently found a source that is half as much as the previous chalk (currently $13.25 for five pounds and free shipping).


Don't be confused that this product is labeled for use in food. Chalk is chalk (chemically described as CaCO3) and when I added this brand of chalk to my paint it behaved exactly like the expensive stuff. The fact that this stuff is used for human consumption might mean it is actually more pure.

Like painters have done for centuries I add chalk to my paint to give it body. Chalk has very low tinting strength so it doesn't make your paint lighter in value, in fact, when you add it to transparent media the mixture becomes almost transparent. I say almost because it does impart a slight milkiness to the mixture. I add chalk both to my oil paints as well as to my acrylics when I need to make a very thick mixture. When you add chalk to acrylics it will make them more absorbent so when you are finished painting be sure to varnish it with a generous coat of acrylic medium.



Although I have experimented with more complex mixtures lately I simply add chalk to my paint or add chalk to Gamblin's G-gel for a thicker medium to oil up my canvas (to see why I do this go here). If you would like more info on more complex recipes go here.

Brad Teare January 2012

14 comments:

  1. This is interesting... you add the chalk instead of the usual impasto or thick gel type mediums people use? Does the chalk give a different effect? And I was wondering how you get the paints consistent... do you add the chalk as you go to paint mixtures while painting??

    I'm assuming you used the chalk in the painting you posted with the moon... it's gorgeous!! I think it's one of my favorites that I've seen of yours.

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  2. The chalk thickens up the paint quite a bit depending on how much you add. I generally add it to the mound of white on my palette to give a nice impasto look to the lights. I might add it to yellows as well for the same reason. But sometimes I just have a heap of chalk in the corner of the palette and add it as needed to whatever color I want to have a nice thick stroke.

    Thanks for the kind words regarding the painting. I did add chalk to the paint in the immediate foreground. You can see it in the pinks of the ground and the light of the green trees.

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  3. Wow, I've never heard of this before. I'm interested in trying it, but I'm concerned about the long term effects this might have on the paint? Will the paint be more likely to crack or peal? I especially like the idea for acrylics. Where did you hear about this?

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    Replies
    1. Rob, chalk is very stable. It has been effectively used for centuries. Rembrandt used it to get his really thick impastos. It is an ingredient in most commercially available impasto mediums (fumed silica is another common ingredient but it is tricky to add on your palette). I suppose it is possible to get the paint so chalky it would lose its adhesion but then it wouldn't stick to your canvas. The only drawback to adding it to acrylics is that it will make your application have a matte finish and it will make that layer of paint very porous. Neither of which bothers me. Especially since I usually put a layer of acrylic varnish over all the layers any way (this is true with the glazes too so the last coat of varnish acts as a unifying layer and all the glazes and chalk layers will cross link making a strong film).

      I elaborate a bit more in this entry: http://bradteare.blogspot.com/2010/10/field-effects-it-has-been-over-year-now.html

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  4. P.S.- I have talked to well respected conservationists and they have reassured me that adding chalk to acrylic will have no long term negative effects. Everyone agreed that it is a good idea to seal the final coats with a layer of acrylic varnish.

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  5. Hi Brad,
    Was not familiar with your work until FASO included it in a post...WOW!
    Love the juicy flowing quality of your work. I'm a pastel and oil painter, so learning about adding chalk is very exciting. Thank you!

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  6. Thank you Christine. Wasn't sure what FASO was until I checked it out. Seems like a great site and I am grateful for their link. I'm playing around with a chalk medium that makes paint like an oil stick. We'll see if I can get that to work!

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  7. Brad I'm glad to see this about chalk I have been making my own gesso by adding extra chalk to primer to get a more absorbent and thick paint. I then paint with very fluid acrylics in a watercolor, wet wash technique.

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  8. This is great! Is this the same as putty powder we get in hardware stores? the thing used to fill gaps in walls etc.?

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    1. Putty powder is water based. So don't add it to oil based paints or mediums. I add chalk to oil based mediums especially prepared for artists to be sure that it remains archivaly sound. Putty powder might have ingredients that could cause the paint to yellow or crack.

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    2. Thaks much for your reply...I thought putty was pretty much chalk. thanks for the clarification.

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  9. Why not use precipitated chalk rather than ground?

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    Replies
    1. I'm not sure what precipitated chalk is. Please elaborate.

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  10. Hi Brad. I am an oil painter. I finally found my particular style of painting but I have come across a problem. My paintings are extremely thick (1/4") all over. They are painted in 1 sitting on gessoed canvas. They look fabulous wet but after 4 months of drying on a flat surface the paint starts to wrinkle. I use approx. 6 part oil paint to 2 parts stand oil....and if the commercial oil paint i use is a bit dry I add a few drops of solvent or linseed oil. I know these paintings will take forever to dry. The wrinkling does look good in my work to a point but when it's all over the canvas not so much.

    As you can tell I am not very educated in painting mediums and would appreciate your suggestions. Could I use chalk to thicken my paint instead of stand oil? I would need to thicken each and every color. I need the paint to be very fluid like oily smooth peanut butter so that it make peaks but spreads easily....so could I add some oil to the chalk and paint? You mention that the final product will be porous so it needs to be sealed...so when should I seal it since my painting could take years to fully dry....and what sealer do you suggest? I can give you my contacts if you ask.

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Thanks for your comments!

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