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  • How to make oil paint thick sticky and ropeyApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2017-06-02 14:48:33 ... Most recent comment 2017-06-15 16:36:18
    Paint Additives Oil Paint
    Question

    ​Greetings,

    I have been trying to modify oil paint for textural effect and my goal is to make the paint thick sticky and ropey/ stringy. Auerbach sometimes seems to have gotten a similar paint quality where the rheology of the paint is highly thixotropic alla Lead White. I've also been thinking of the quality of silicon caulk as the texture I am after. 

    I have expeirmented with adding stand oil, dammar, clay made into paste, alkyd, etc but these tend to 'shorten' the oil, lowering the viscocity (with the exception of the clay). My next step is to see what marble or glass powder does. I have a (Daniel Smith) tube of transparent blender made with alumina hydrate that is perhaps the closest I've found for the texture I am after.

    Any suggetions for this type if paint modification would be helpful. 


    Thank you!

Answers and Comments
  • EditDeleteModerator Answer

    ​You might get close to the results you describe by adding 10% by volume marble dust and some stand oil to factory-made titanium white. Blend on a glass slab until homogeneous, work with a glass muller, then introduce  a small amount of stand oil with the knife. The resulting mixture will be long and ropy with distinct ribbons. (There is a PDF instructional on the Utrecht site with pictures. If the other Moderators don't object, I'll link it in a subsequent reply. There are no product links in the document.)

    Matthew Kinsey, Utrecht Art Supplies
    2017-06-02 16:41:13
  • EditDeleteModerator Answer

    Matthew, you are welcome to post the link.

    As to the question. The answer really depends on what paint you are attempting to modify and exactly what handling properties you are searching for. Most commercially available paints have added enough modifier (aluminum stearate, castor wax, aluminum hydrate) to create a short buttery paint that is similar in feel across the paint range. When modifying these you need to add enough of the material (and likely extra oil) to surmount the action of the original modifier. Matthew’s suggestion may work for what you want. I have made handground lead white oil paint that was extremely ropey by admixing some barium sulfate and a bit of extra linseed oil into the paint while I was mulling it. The consistency was both dense and ropey at the same time.

    If it were me, I would probably mull up a number of additives in oil to a loose constancy and experiment with each of these by adding them to my white to determine which created a paint with the rheological properties that most closely resembled what I was searching for.

    Please report back and let us know what worked for you.

    Brian Baade
    2017-06-02 19:39:23
  • EditDeleteModerator Answer

    Thanks, Brian. http://images.utrechtart.com/Content/pdf/experts_archive/studiocraft/Long_Bodied_Oil_Paint.pdf

    Also, for artists reading this who don't yet know how to manually fill paint tubes, this is very useful when working in batches: http://images.utrechtart.com/Content/pdf/experts_archive/studiocraft/tubing_mixtures.pdf

    In addition to the widespread use of stabilizers/amendments,  I think the very small, uniform particle size of modern, precipitated pigments may also have something to do with the texture of today's factory-made whites, compared to what is seen on historical paintings. (Other Moderators will likely know more about this than I do.)

    Matthew Kinsey, Utrecht Art Supplies
    2017-06-02 21:03:52
  • EditDeleteModerator Answer

    There is ample evidence that Dutch process stack lead white paint behaves in its very characteristic manner due to the diverse, heterogeneous morphology (as well as larger size) of the pigment particles as well as its chemical reactivity with the oil medium. I know of two (periodically, three) manufacturers who make old style lead white. It is interesting to experiment with these but you may certainly find a paint that affords you the tactile and physical effects you are looking for without resorting to such rarified materials; and I mean no disrespect to those materials, I have stockpiled a substantial stash of them just in case these manufactures stop production.

    Brian Baade
    2017-06-02 22:44:01
  • EditDeleteModerator Answer

    ​Also, Matthew, thaks for the tubing primer.

    Brian Baade
    2017-06-02 22:44:50
  • ApproveRejectUn-ApproveUser Comment

    ​Matthew and Brian,

    What luxurious info, thank you and I will keep you posted. I have read that larger pigment size does alter paint rheology but am not well versed here. 

    Is there a chart you may know of that lists approximate pigment size across common pigments? 

    Or other charts that list other rheology properties? (And what are the properties of rheology with respect to oil paint?) I've seen some drying rates or oil absorbtion  rates (Doerner) arranged like this. 

    I'm sure this varies by many factors (mulling, brand etc), and perhaps too many to be useful, but can imagine flake white or ochre being on one end and phthalocyanine and the lakes on the other, giving me an idea of pigment-behavior-properties to explore other colors beyond white...

    Best!

    2017-06-03 13:20:51
  • EditDeleteModerator Answer

    Most modern oil paints exhibit short pseudoplastic flow (described as short, buttery paint) due not only to the homogeneous particle size and shape of pigments, but also to additives typically used in these paints.

    Oil paints made from pigments of heterogenous particle size and size exhibit different types of viscoelastic flow. At Natural Pigments we have measured a wide variety of pant behavior, including viscoelastic; time-dependent viscosities, such as rheopectic (viscosity increases with duration of stress) and thixotropic (viscosity decreases with duration of stress); and non-Newtonian viscoelastic flows, such as shear thickening (dilatant) (viscosity increases with increased stress) and shear thinning (pseudoplastic) (viscosity decreases with increased stress). Chemical and physical interactions between pigments and drying oil gives rise to incredibly complex and often surprising behavior. Although additives are used in very small amounts in professional-grade oil paint—usually less than 2% by weight of the pigment—their effect on flow is dramatic since the additives are adsorbed to the surfaces of pigment particles.

    Bodied (partially polymerized) drying oils impart long flowing behavior to paint that is also described as “sticky” or “tacky”. This is due to the large molecular weight of polymers. Adding bodied oil to oil paint can often accomplish what you are seeking. Grinding barite (barium sulfate) in a blend of bodied oil and refined oil and then adding this mixture to your paint is also useful and also does not thin the paint.

    Basic lead carbonate (lead white) in drying oils with low or no free fatty acid creates long, ropey paint. Oils with free fatty acid, especially above an acid value of 4 or 5, create the opposite. We have found highly variable paint flow from lead white made according to the stack process or “old Dutch method”. These paints exhibit different flows depending on the particle size and crystalline forms of the pigment.

    George O'Hanlon
    2017-06-03 14:14:57
  • ApproveRejectUn-ApproveUser Comment

    Thanks again for all the "rheological" suggestions here everyone.  I'm really learning some new ways to describe and think about 'non-newtonian' paint consistency- a real vocab primer George!

     I will look for some barite to try as well. I got some nice thick, firm, long, and stringy results from the addition of powdered marble and Stand Oil to a tube of Titanium White like I was after, as seen in the photo.

    However, the 10 percent addition suggestion didn't affect the paint enough, and I had to add much more than that, which led to the paint being too brittle for use once dry…

     LongTitWhite.jpg

    2017-06-15 16:36:18
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