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Old 08-26-2019, 03:25 AM
tidal tidal is offline
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diy ingredients to thicken paint?

I know how to thicken acrylic myself and also available products on shelf for it but was looking into how to thicken oil paint due to acrylics when thickened allways looking like plastic any water based acrylics with a thickness or gloss to them just found them horrendous to work with and look at even the more expensive brands! so am use the paint that I using for whites and apply thinly will be acrylic . However the thicker colored layers (that will not be influenced by the yellowing of oils) I am use oil as oil suspends that pigment so beautifully no plastic look there) But I had looked up an old thread about this but most suggestions were shop bought and some no longer sold or not sold in the UK no one suggest homemade.I know you can use beeswax BUT this won't work as I want to be able to sand it back..Maybe is not such a thing is possible as it seems to be a lot of butters etc.You can "suck" out the oil with paper towels cardboard etc but then they loose the oil which is holding the pigment in such a beautiful way.
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Old 08-26-2019, 05:31 AM
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vhere vhere is online now
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Re: diy ingredients to thicken paint?

tissue, sand and sawdust are things I've used at times

I tried the fluff out of the tumble drier but didn't work well
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Old 08-28-2019, 10:51 AM
tidal tidal is offline
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Re: diy ingredients to thicken paint?

yeah this I know but thankyou all the same was meaning to create smooth thick paste like to almost sculpt on the paper canvas etc there is stuff out there on the shelf but I like to experiment and is interesting to hear what others do or have tried aside from the tried and tested
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Old 08-29-2019, 06:25 PM
contumacious contumacious is offline
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Re: diy ingredients to thicken paint?

Fumed silica does a great job at thickening oil paint without making it too stiff. It will hold brush and knife marks well once you get the right ratio. Follow the safety instructions, wear a respirator when mixing it in and when sanding the dried paint. Calcium Carbonate / Chalk / Marble Dust will thicken oils as well but it ends up more putty like rather than the thixotropic gel consistency you get with fumed silica.
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Old 08-30-2019, 05:52 AM
tidal tidal is offline
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Re: diy ingredients to thicken paint?

Thanks for that I had been thinking about silica in the past


please note anyone who intends to mix the raw powder form of silica into there oil binder pigment etc MUST wear a respirator suitable for toxic dusts JUST whilst mixing in as powder apparently floats about in air in powder form when agitated.It is not however apparently very thixotropic according to my research but I guess experimentation is the name of the game



also a extract from tad spungeon site " This depends entirely on the consistency and ingredients of the putty, paint can be made with any degree of mobility or adhesion. A chalk putty is more thixotropic and mobile than a marble dust or whiting putty. Putty can be used quite densely with bristle brushes, or more finely with softer brushes. "he personaly prefers a paste which he makes with stone dust. Chalk ,Marble dust can be added to make own version or preferred VISCOSITY the two later mentioned ingredients are more thixotropic.
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Old 08-30-2019, 10:26 AM
contumacious contumacious is offline
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Re: diy ingredients to thicken paint?

Quote:
Originally Posted by tidal
.It is not however apparently very thixotropic according to my research but I guess experimentation is the name of the game

The terms Pseudoplastic and Thixotropic kind of confuse me and are often used incorrectly, so I am going to ignore any terms and just describe how a gel made with linseed oil and fumed silica behaves with a knife or brush compared to a putty or gel made with various types of calcium carbonate. I found just the opposite of your statement above, as far as achieving the type of gel I wanted with linseed and walnut oil. Additionally from my research, fumed silica appears to be the number one choice for getting a non sagging / non self leveling liquid in non "art" areas, particularly with epoxy resins - those talking about it use the term thixotropic to describe what it does.

What I want is a gel that is very easy to manipulate but not flowing / self leveling like maple syrup. I want it to hold sharp edges and peaks created with a palette knife, the same, plus brush marks when using a bristle brush. Once created, I want the shapes to stay as close to the way they look once executed without moving, softening, leveling, running. Nothing I have tried gives that better than fumed silica and oil.

Though I have not tried any real chalk dust, I have tried other fillers made from calcium carbonate. I am guessing that the reason chalk apparently behaves differently than ground calcium carbonate is because the particles are more like fumed silica. I found it impossible to create a gel that behaves that way with those fillers at any ratio using any type of oil. When enough filler was added to make it keep its shape, it became much too stiff to respond easily to a brush or palette knife. When thin enough to brush / knife easily, it became too self leveling, losing all the nifty textures I created, slumping down into a smooth puddle. I also found that adding any type of alkyd resin / medium to the gel made it self leveling / slumping, so the only dryer I add to mine when needed is CoZiCa or some similar metallic dryer, which did not destroy the nature of the gel if t was added while mixing in the fumed silica. If you add some dryier after reaching the perfect state, it can make it too runny, forcing you to add more fumed silica to balance out the added liquid.

A fumed silica gel does shrink more than a putty heavily filled with calcium carbonate, so don't expect to be able to build up 1/4" and thicker surfaces with it. It is best suited to lower height strokes. There are probably better materials to use than oil based gels or putties for thick applications. You could add oil paint on top of the sculpted surfaces to get the more appealing look of oil paint that you want.

FYI, Glass Microspheres might be a better choice if you want to sand it. One page said that fumed silica is not a good choice to use if you plan to sand it down.

Maybe your perfect gel could be made using a combination of two more materials such as fumed silica and glass microspheres, or maybe fumed silica and calcium carbonate, all three or some other combinations entirely.

https://www.youtube.com/watch?v=kI6AdYPRswM

Last edited by contumacious : 08-30-2019 at 11:05 AM.
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Old 08-31-2019, 05:43 AM
tidal tidal is offline
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Re: diy ingredients to thicken paint?

Understood you are after the first stroke you have made with your brush or knife to remain as it is .Personally I like the way once the medium has been put on there and have applied with brush/knife etc that you can then change that first shape of that mark when the medium is agitated it can be further manipulated allowing one more playtime !by this is what for me is meaning of thixotropic. Anything sanded is a no no to breathe as is airborne I always wear a mask.But thankyou for the heads up about silica as I want a thicker consistancey.I had never heard of the glass microspheres that is an awesome bit of advice which I will follow many thanks for that Contumacious
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Old 09-01-2019, 08:34 PM
contumacious contumacious is offline
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Re: diy ingredients to thicken paint?

You are welcome.



Quote:
Originally Posted by tidal
Personally I like the way once the medium has been put on there and have applied with brush/knife etc that you can then change that first shape of that mark when the medium is agitated it can be further manipulated allowing one more playtime !by this is what for me is meaning of thixotropic

FYI, fumed silica gel does exactly what you describe there as well. Endless manipulation is possible (until it starts to dry) without it flattening out like calcium carbonate mediums do. Unfortunately nobody sells any that has very much body to it, you will have to make your own to experience it. Fortunately the fumed silica is fairly inexpensive.

Fumed Silica in Linseed Oil = Whipped Cream or non sticky meringue like material that moves easily and holds the shape well when moved about repeatedly

Calcium Carbonate in Linseed Oil = stiff maple syrup like stuff that keeps moving after you stop moving it - slumping down and losing the shape you gave it.

Neither one is going to be particularly good at building up thick textures like a modeling paste, but the fumed silica gel is king when it comes to crisply executed impasto techniques from my experience. I have not been able to find a video that shows how the stuff I make behaves, but this page does give a hint of what it is like:

http://chasingthedesertsky.blogspot....ed-silica.html

The 3rd from the last photo is what happens to oil mixed with calcium carbonate to some extent as you work with it - it self levels, undoing all your work. The 2nd to the last photo is what fumed silica gel behaves like after you stop moving it about - it stays in the same shape you left it.

From your responses it seems like I am not describing things well enough for you to grasp the difference, but then, maybe you are. Though I have never posted any videos anywhere, I might upload one showing what I am talking about.

Last edited by contumacious : 09-01-2019 at 08:49 PM.
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