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-   -   Casein Opacity? (http://www.wetcanvas.com/forums/showthread.php?t=1463423)

laika 03-20-2019 12:59 PM

Casein Opacity?
Is casein paint inherently opaque, or opaque by tradition? If transparent pigment were mixed with with casein emulsion, would a transparent casein paint result?


llawrence 03-20-2019 01:11 PM

Re: Casein Opacity?
In my (admittedly limited) experience, casein is opaque. Colors that appear semi-transparent when wet (ultramarine, phthalo blue) opaque up as they dry.

laika 03-21-2019 05:23 PM

Re: Casein Opacity?
Thanks, llawrence! Hmmm... Pthalo blue is pretty transparent. I wonder why casein fixative goes down transparent but the paint is usually referred as opaque?

Trikist 03-21-2019 10:20 PM

Re: Casein Opacity?
1 Attachment(s)
Casein becomes lighter and more opaque with drying. I have to use black to get darker versions of colors rather than relying on transparency. I am not sure what is different about black. If you varnish caseins they have darker values but are still not transparent. Example below:

Attachment 864525

Trikist 03-21-2019 10:35 PM

Re: Casein Opacity?
1 Attachment(s)
If you spread a normally dark color thin enough, you can get a mild translucent look but not like watercolors. These are Shiva Caseins. I have never tried to make my own. Gary

Attachment 864526

laika 03-21-2019 11:47 PM

Re: Casein Opacity?
Thanks, Gary! I guess it's some kind of strange chemistry between casein and the pigments.

I painted something recently with opaque pan watercolors, using a strong mix of Spectrafix fixative from concentrate to wet the pans. In the process, I learned quickly that I don't know how to paint opaquely.

Trond 04-15-2019 10:36 AM

Re: Casein Opacity?
Casein can be tricky to figure out at first. I wouldn't say that you can't use them transparently, but they are definitely on the more opaque and brighter side of things. They brighten up even more than gouache. Like Trikist mentioned, you're likely to use black more often than in other media. I recommend having a test sheet of paper next to you, to check out how colors look when dry.

Delofasht 05-11-2019 12:03 AM

Re: Casein Opacity?
Tricky indeed, while they grow more opaque as they dry, they also become more matte looking. They can be buffed after cured to a glossy look though, and can be used in a very transparent manner by adding very large amounts of water to paint ratios. It is surprising how strong the film is even when diluted by up to 95% water to paint ratios (depending on the surface preparation).

At that level of dilution they are quite transparent, but building up can be tricky then because a paper surface will want to buckle. On a traditional gesso primed panel though, I have found I can build up watercolor-like glazes of color pretty efficiently. They remain fairly transparent at that dilution level, and seem to adhere a bit better than Watercolor would (still having a very slight film of Casein affixing them to the surface).

One can also increase the transparency by adding more of the Casein binder itself, which works to keep the paint body more, it is similar to adding a few drops of oil to oil paints (or adding “clear” acrylic mediums to acrylic paint). This makes the paint a bit more mobile and transparent, but not at the cost of making glazing more difficult (as can happen with extreme water dilution).

laika 05-11-2019 01:33 AM

Re: Casein Opacity?
Thanks for reaching back to this, Delo! Plenty of good info in what you shared.

How long before you consider a painting or layer cured?

Delofasht 05-12-2019 11:06 AM

Re: Casein Opacity?
When working in thin glazes, they can be layered after becoming touch dry, but like watercolor are easily reactivated so one has to apply those carefully and not scrub the next layer in.

I consider a painting or layer as cured in about a week or two (depending on your humidity levels and ambient temperature), this can sound like a long time to wait between layers, but is easily solved by having multiple paintings going at one time. After a week of summer here in the east US with minimal rain, my Casein work is usually ready to be buffed without much, if any, color coming off but becoming quite glossy after the buffing. I have a test page available from a few years ago that is not fully buffed, I will see if I can find it and snap a pic then buff it and get another to see the difference in color. Unfortunately it was intended to be a thick and direct application of color, so I cannot show off the transparency effects very well... maybe a bit of the lighter colors over the darker will show it though. Be back with it in a couple days (it is in storage).

laika 05-15-2019 10:37 PM

Re: Casein Opacity?

Originally Posted by Trond
I recommend having a test sheet of paper next to you, to check out how colors look when dry.

Thanks, Trond! That's a great and very practical idea.

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