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Re-Grinding Geneva Pigments

SummerSummer -
edited April 26 in Studio & Supplies
Has anyone tried to re-grind Geneva pigments that have dried in the tubes?  I'm thinking of re-grinding hardened Burnt Umber with a glass muller and some refined linseed oil.  I have recently learned how to add air before shaking the tubes just before use and how to squeeze air out just before closing the caps for storage to keep paint from hardening for the future, but I still have a large amount of Burnt Umber that has solidified in a tube that I would like to re-work and put into a few empty paint tubes that I have on hand.   

Comments

  • Summer

    Interesting. Keen to hear of the outcome. 

    Because the pigment is now bonded with a polymer resin i.e. tube paint with a drying oil, I don’t think it will be released by a muller. A gritty mix of oil and bu will have no coverage or mixing strength.

    Heat and Turps may partly dissolve the dry paint.

    Denis

  • Summer

    on line research indicates that reverse polymerisation can be achieved using microwaves in a nitrogen atmosphere. 

    Denis

  • SummerSummer -
    edited April 26
    Thanks, Denis.  I thought I'd try it because I am not sure what the additives are in Geneva.  If I ever knew, I have forgotten.  And, a gritty mix is the usual complaint of people who have tried this and the reason it didn't work for them.  Where is a physics or chemistry lab when you need one!  I will give it a try on a very small sample, "Heat and Turps", just because I'm curious, but I'm not hopeful.  Summer   
  • SummerSummer -
    edited April 26
    dencal said:
    Summer

    on line research indicates that reverse polymerisation can be achieved using microwaves in a nitrogen atmosphere. 

    Denis

    Thanks, Denis, but it's beginning to look like too much work, isn't it.  I ordered another tube of Burnt Umber from Geneva today.  For the future, then, I will continue my new method of adding and releasing air from the tubes as I open and close them.  That should help a bit.  Summer 
  • Keep a little BU on hand in a snapcap, store the remainder of the tube in refrigerator? Use a tube winding key to get the air out?
    Summer
  • Will Geneva replace the dried paint? Free?
  • SummerSummer -
    edited April 27
    Thanks @BOB73.  I'll do those things as well as soon as the Burnt Umber gets here.  I have all three items in my studio--snap caps, refrigerator, and tube winding key.  By the way do you have any thoughts about the oxygen exchange in the plastic of the snap caps?  Does this concern you?  Is that why they don't have  a longer shelf life you think?  I could begin double wrapping them and place them in the refrigerator with the other paints.  Summer   

  • BOB73 said:
    Will Geneva replace the dried paint? Free?
    I didn't ask because I had already used about a quarter of the tube already.  I have some friends  with access to labs that might be able to help me with what Denis suggested--microwaves and nitrogen.  Summer
    BOB73
  • RE: "oxygen exchange in the plastic of the snap caps" Snap caps come in a very large variety. I'm sure they are all liquid proof but I'm also sure they are not all air tight. The only thing we have to go by is how difficult they might be to open and close and greater difficulty doesn't guarantee performance. It's all "trial and error". If they are air-tight I don't think any chemical reaction within the container will produce an oxygen exchange on the molecular level of enough significance to affect the paint. As for the tubes, They are vinyl and remember their shape so when you squeeze them leaving a dent in the side they want to return to their original shape. The only thing preventing this is the vacuum created in the tube if you closed the lid while squeezing the tube. If the dent disappears after a day or two, the tube has lost its vacuum and the pesky old oxygen has found a way in.
    Summer
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