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MITRA Forum Question Details

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  • rheology of painting for glazingApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-11-30 20:46:58 ... Most recent comment 2019-12-02 12:40:11
    Oil Paint
    Question

    ​Hello Mitra,

    I always see people watering down there paints when they are going to make a glaze.  Many books talk about avoiding this bc if one goes extremely past the CPVC this will create an unstable film.  Is there a way to guage the making of paint for a glazing technique?  Is there some sort of general rule or rule of thumb that one should take into account when mixing paint for a glazing technique? 


    Best Regards,

    Hector 



Answers and Comments

  • EditDeleteModerator Answer

    ​While some oil colors have enough oil to reduce simply with solvent, most will be reduced too much to retain the critical optical function of oil in the glaze. Generally, application of paint in thin "washes" with solvent alone tend to settle in a dull, lackluster layer that is weakly bound and lacks optical clarity. Viscosity is important in glazing, because the consistency must preserve pigment suspension, but also allow manipulation and removal while wet. A small amount of bodied oil (stand oil or sun-thickened linseed) to the medium lends this property, but too much makes the paint sticky and difficult to distribute and wipe away.  A good glazing medium should also have enough tack to prevent beading. Composition of the underpainting is important here too- colors need to be resistant enough to wipe clean, if necessary and to resist staining from subsequent layers. 

    Matthew Kinsey, Utrecht Art Supplies
    2019-12-01 11:31:01
  • EditDeleteModerator Answer

    One method of preparing glazes from modern commercially-prepared oil paint is to add low-refractive index white pigment—commonly referred to as "extender pigments" or "fillers"—to the paint. While this increases the pigment volume concentration (PVC) of paint, a small amount of oil may be added to maintain the paint near its critical pigment volume concentration (CPVC). Pigments of low-refractive index, i.e., chalk, silica, kaolinite, etc., do not absorb or scatter light as do color pigments or high-refractive index white pigments, and hence appear translucent in oil paint. These were commonly used to extend paint by the old masters and can be used to create glazing tints with color pigments. Extender pigments also alter the rheology of paint to provide interesting behavior in their flow and brushing properties.

    George O'Hanlon
    2019-12-01 17:57:20
  • ApproveRejectUn-ApproveUser Comment

    ​Thank you Matthew and George. 

    I have 2 more related questions connected to this subject.

    The Italian and northern renaissance masters had a direct connection to the tempera paintings being made in the studios in which they studied and worked.  I think of Leonardo and his important connection to Verrocchio and Lorenzo di Credi.  

    I mention this because egg tempera can have a consistency thats closer to that of water.  Can there be any truth to the idea that some masters had there paint for glazing similar to the consistency of tempera?  If this is true isnt this damaging once one takes into account the CPVC of the colors?


    2019-12-02 12:40:11

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