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  #11  
Old 22-02-10, 11:14 PM
Alessandra Kelley Alessandra Kelley is offline
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Also, the thread on toxicity that Koo mentioned can be found at http://www.eggtempera.com/forumnew/s...&referrerid=13

(assuming I've got the tech tools right)
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  #12  
Old 23-02-10, 09:49 PM
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Koo Schadler Koo Schadler is offline
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Hello Joanne,

I agree with Alessandra - your colors are beautiful, and the rendering is very good, particularly given that it is difficult to create smooth transitions in tempera. I also agree with all that Alessandra wrote about pigment pastes. The only thing I would add is my personal preference for a pigment paste's consistency, which is to have it toothpaste-like. Some pre-made pastes (dispersions) are more akin to heavy cream, and I like things a little thicker so I can make a slightly denser paint when necessary (although I primarily work with thin washes, once in a while a more covering paint is needed).

You had asked for my gesso recipe in another posting, Joanne, and its too long to print here - but if you send me an email (info@kooschadler.com) I'd be happy to forward it to you.

Koo
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  #13  
Old 23-02-10, 09:50 PM
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Koo Schadler Koo Schadler is offline
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PS - Thanks for helping me with that toxicity thread business Alessandra.
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  #14  
Old 23-02-10, 10:21 PM
ms wings ms wings is offline
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Alessandra: Thank you for your uplifting critique of my painting. I needed that!

Thank you as well for your information on how much water to add to dry pigments. Can you tell me if marble works well for mixing the pigment and water. Is it better to use glass. I have a marble slab I could use and alieviate the cost of the glass. I definitely understand your comparison to hot cocoa. You say you keep your pigment paste jars under a lot more water. To what are you referring? Thanks again, Joanne
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  #15  
Old 23-02-10, 10:43 PM
ms wings ms wings is offline
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Hi again Koo. Thank you for your generous critique of my painting. It means a great deal to me.

I will send an e-mail for that gesso recipe. I saw a dry Gamblin's gesso for sale I believe at Dick Blicks. The ingredients are: rabbit skin glue, gypsum, marble dust, and titanium dioxide. Do you know if that dry mix is comperable to your recipe, and how many panels can I do with a one pound box? The description says it has an oil binder and I wonder how the tempera would adhere to it. Thank you again for all your help and critique. Joanne
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  #16  
Old 24-02-10, 12:44 PM
Alessandra Kelley Alessandra Kelley is offline
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Oo, don't paint with tempera on an oil-based ground.

As for pigments under water: Cennini in his medieval how-to manual says to keep pigments in containers with extra water over them, and it's pretty good practice. Pigment pastes can dry out before you know it, especially if your jars are not absolutely airtight (and most of them aren't); and regrinding them is a royal nuisance, since they've usually compacted into a brick that needs to be re-pulverized. Also straight pastes can be susceptible to mold (covering them with water doesn't prevent this, but it seems to happen less often).

I've followed this practice for years, grinding my pastes, putting them in jars, then pouring a layer of water over them. It doesn't water down the paste especially, and it keeps them in good order, and I don't have to worry about exactly how much water I use in the initial grinding. If the water evaporates I can easily see and replace it. If I want an especially thick color (titanium white is the most commonly needed for this, since it needs to be pretty thick to get solid clean white lines), I mix up some paint in the morning and use it in the afternoon.

Both marble and glass are fine for grinding pigments. Marble is a little softer, but unless you're pulverizing your own pigments from especially gritty minerals it shouldn't make much of a difference.
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  #17  
Old 24-02-10, 01:08 PM
dbclemons dbclemons is offline
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Quote:
Originally Posted by ms wings View Post
...Gamblin's gesso for sale I believe at Dick Blicks. The ingredients are: rabbit skin glue, gypsum, marble dust, and titanium dioxide. Do you know if that dry mix is comperable to your recipe, and how many panels can I do with a one pound box? The description says it has an oil binder and I wonder how the tempera would adhere to it. ...
I think you misunderstood the description. It couldn't be a dry mix if it contained any oil.
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  #18  
Old 24-02-10, 03:03 PM
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Koo Schadler Koo Schadler is offline
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David is of course correct - a dry gesso mix wouldn't have oil. I believe Gamblin offers two kinds of ground: a traditional gesso ground, the one you initially described Joanne, that is suitable for tempera; and an oil painting ground that has the addition of an alkyd resin. Don't use the latter - tempera won't adhere properly.

The ingredients for traditional true gesso are pretty much always the same: an aqueous animal glue + an inert white substance (either chalk or gypsum) + water - and perhaps a small percentage of titanium to increase the opacity. That's it. What differs from one recipe to another is (a) the quality of the ingredients, and (b) the ratios between them. The most important ingredient is the glue, which ideally should be of very high quality. A good glue should be clean, pale in color, and smell sweet (not rotten) when hydrated and warmed. I checked out Gamlbin's rabbit skin glue a few years ago and it was very good, as is their practice.

The second consideration is the ratios between your glue and inert white substance. There are a lot of different "recipes" for gesso. A higher percentage of glue to chalk or gypsum makes a harder gesso. A lower percentage of glue gives a softer gesso. There is some room for play, but at some point a gesso can have too much glue and get too hard (and crack) or have too little glue and get too soft (and crumble). A premixed formula such as Gamblin's has already figured out the ratios for you. This saves you that step, but doesn't give you choice either. Gamblin is such a good company that I would expect them to have a good recipe for their gesso. (On the other hand, I tried Fredrix's premade formula many years ago. The quality of the glue seemed poor, the gesso came out hard, and it was prone to cracking. I haven't tried it for years - the may have changed). So if you are going to make gesso from premixed formulas, its best to ask for a sample of the glue they use, to see its quality, and to pay attention to the quality of the surface that results.

And most importantly, and this is true for any gesso, never over heat it. Above 135 degrees (I think it is...) the glue starts to break down and this can lead to cracks. A good gesso (made with good glue) will dissolve readily in a double boiler (but never put the glue and double boiler on the burner; first heat the water in the d.b., then take the d.b. off the burner, then stick the glue pot in the d.b). A good way to test the temp of your gesso is that you should be able to stick you finger in - it should feel nicely warmed but not burn.

Not every one loves it, but gesso making can be a meditative, satisfying process. Have fun.....

Last edited by Koo Schadler; 24-02-10 at 03:18 PM.
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