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  • oil paint mediumApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2017-11-18 16:16:32 ... Most recent comment 2017-11-25 08:49:15
    Paint Additives Paint Mediums
    Question

    ​I usse oil glazes over a monochromatic egg tempera underpainting.tand Oil (1part Sstand Oil and 6 parts english turpentine) is not satisfactory. Normally my woerk requires 3- to 40 very, very thin oil glazes. Can you recommend a workable reciepe? Alklyd and other such "synthetic materials" are not satisfactory for me.

Answers and Comments
  • EditDeleteModerator Answer

    Hi

    I know from a forwarded correspondence that your primary issue is the slow drying rate of your oil glazes. I applaud you for refraining from adding large amounts of soft resins to your mixture to speed up the setting of the glazes. This is a common, but lamentable, practice (see our "Resources" section for more info on this subject). I do wonder how much medium you are adding to your paint to create glazes. It is good painting practice to only add enough medium to make a paint that can by physically manipulated to a thin glaze and not to dilute the paint with so much medium that you create a “watercolor-like” wash. I will assume that you are adding a reasonable amount of your stand oil-turpentine mixture.

    My first response to a query like this would be to suggest an alkyd medium. You have made clear that you are not interested in that. I also know from your previous email that you do not trust this medium. I am not going to try to persuade you here but feel the need to comment on this for the benefit of others that will read this thread. Oil modified alkyd resins have been in use since the 1920s and have stood the test of time. They remain more flexible over time than oil paints and paints that incorporate them are less soluble to the action of organic solvents than a paint that contains only a drying oil in the same proportions. This is a separate issue than if one does not like the feel or rheology of paints containing alkyd medium. Honestly, I never liked the feel of oil paint with an added gelled medium. I have less of a tactile objection to fluid alkyd mediums.  

    Anyway, alkyds are out for you. I wonder if you could substitute a faster drying bodied oil (homemade sun thickened oil comes to mind) for the very slow drying stand oil.

    If you really do like the stand oil/turp mixture and only object to the dry time, I wonder if it would not be a good idea to just add to your medium a few drops of cobalt drier, or even better a system drier (a mixture of metal salts known to accelerate the oxidation of oil films).

     I generally do not recommend that artists add driers to their paints and mediums because it is way too easy to add more than necessary and risk compromising your paint film over time. If you performed systematic tests and only added just the amount necessary to make a glaze layer that dried in a reasonable amount of time (a couple of days) this should be safe. If it were me, I would make up a batch (eg 8 oz) of your dilute stand oil medium and add a few drops of drier. Then add this to a blob of paint and create a typical glaze. Test how many days this takes to dry. If it is still too long, add another couple of drops and try again until you figure out the proportions necessary to create a glaze that meets your requirements. Do not add more than necessary.

    I hope that this was of some help. Feel free to post a response if I somehow missed the point of your question. Additionally, others may have suggestions that I did not think of.

    Brian Baade
    2017-11-18 18:42:30
  • ApproveRejectUn-ApproveUser Comment

    ​I've done a lot of oil glazing over egg tempera.  My experience is that oil mediums dry more slowly atop egg tempera and traditional gesso; I've seen drying times double or triple (compared to how the same oil glaze dries over an oil underpainting and ground).  My thinking is that the high PVC (pigment volume concentrate) and porous surface of egg tempera and traditional gesso allow the oil medium to sink in, making it less well exposed to oxygen, making it slower to cure.  I don't know if this is correct, but so far it is the only reason I can think of to explain the consistently (at least, for me) slower drying rates of oil glazes over pure egg tempera.

    If this is holds true for you, I can think of two possible solutions.

    1. Give the egg tempera time to polymerize (3 months or more), then polish the surface a bit to cut back on the porosity/absorbency.  I've found that oil glazes (and varnishes) sit much better (i.e. there is much less sinking in) a top a cured and slightly polished egg tempera than on freshly painted tempera.  

    2. Apply a isolating layer over the tempera before moving onto oil.  There are many possibilities for isolators (which I've talked about in another post: https://www.artcons.udel.edu/mitra/forums/question?QID=151).  There are pros and cons; it's not a settled issue how best to isolate egg tempera - but in my 25 years of experience (which I appreciate isn't long in the conservation world) I have the most success with a very thin layer (1 part shellac to 6 or 8 parts solvent) of bleached, platina, de-waxed shellac.  

    If any of the above is applicable to you, or helps with your method, I'd be most interested in hearing about it. 

    Koo Schadler

    2017-11-25 08:49:15
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