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Old 01-04-07, 06:58 PM
Patricia Lynch Patricia Lynch is offline
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Default Cracking in panels and egg tempera paint cracking

Cracks appearing in the ET, rather eratically across the panel and some faults inthe gesso panels.

Can anyone help please I have never had a problem with either cracking of gesso or cracking of ET paint until the last couple of months - I made some new panels using 25 ml plywood which we had had in the outdoor shed for quite a few years , we brought it in to dry - then my husband cut it and I sanded and applied washed muslin and 8 layers of gesso - I added some flow aid, which I have never used before to the gesso on the advice of the gesso making section of this website - that was the only different thing used on this occasion and first of all had problems with cracks in the gesso with one panel actually partly delaminating - this has never happened to me before but I have never used ply before or added flow aid and wondered whether it could be either of these two things.

Secondly, when painting on the reasonably good panels - I then had the painted surface crack into fine crackle glaze type patterns but not all over just in certain areas - any idea what's going on please??? :-(

Depressed of High Wycombe
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Old 01-04-07, 07:11 PM
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Bert Congdon Bert Congdon is offline
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I have been over this Many times, and many people argue with me.
Would you like me to go over it again?
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Old 02-04-07, 12:56 AM
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I can't recall reading it and would like to. Maybe you could just paste the answer back in here or give a link.

jeff
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Old 02-04-07, 03:07 AM
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Bert Congdon Bert Congdon is offline
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I too use plywood. I cut a piece of linen or cotton the size plus about 4 inches all around. I mix carpenters' glue from animal glue. This is made by puting the animal glue in a can, adding just enough water to cover the glue, and with a large brushslop a coat on the wood and a coat on the canvass. Make plenty. Be certain you have enough before you start. Now slap the canvass on the wood. DO NOT COAT THE WOOD with a sealer There is no coating that animal glue will stick to. Squeeze out the excess glue and bubbles. I have a pieces of plastic I buy in paint stores made for smoothing out wallpaper, but the plastic case your CDs or DVDs come in will work just fine. I wrap it around onto the back and staple it so it won't curl up when it dries. Now you won't get cracks from wood expansion and contraction.

Mix your regular water and glue and chalk the way you usually do, but add one glug of glycerine. This does not effect the strngth, but make it flexable. If you don't want it to be resoluable in water add a teaspoon of
alum. Now if it cracks, you gesso is too rich with glue. I put on 4 or 5 coats, scrape it down with a piece of glass, and sand it. You don't have to wait for each coat to dry. You can recoat as soon as it loses it wet shine.
Under no circumstances should you put the glue in the refrigerator over night.
It becomes smoother, but very weak. Now you can gaurantee it for five hundred years like I do.
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Old 02-04-07, 03:11 AM
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A glug is one or two tablespoons depending on how big your batch is. Let me also say that you should let your gesso dry slowly. Never stand them on end as the water will drain to the bottom, and it will dry out at the top causing cracks along the top. I make mine dry slowly by laying them down and covering them with plastic. I do about eight at time. About twice a day I lift the plastic and air it out. I turn it over then and place it back. I do this for two or three days. This is self taught after many failures. Never lay it in the sun, and never force dry it in any way. Be sure a hot air register is not blowing on them.
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Old 02-04-07, 01:55 PM
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What's a glug?
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Old 02-04-07, 02:22 PM
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Sorry that got in above yours Jeff.
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Old 02-04-07, 03:50 PM
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Patricia,
I'd stick to the recipe and support that you used previous to the cracking.
I never use flow aid, I would never use plywood. I just use MDF, no need for linen.
Rob
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Old 03-04-07, 09:50 PM
Alessandra Kelley Alessandra Kelley is offline
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I have had bad experiences with plywood, even good grade stuff. It cracked badly along the grain. I think it must be something to do with the way plywood is bent out of its original round shape in the first place. Thankfully it was mostly just experiments.
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Old 04-04-07, 01:42 AM
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I've had plywood start to do cracking as well. I think that maybe only marine grade plywood might be OK to use. I know that on our little boat it doesn't crack in the same way even after a lot of exposure to water.

jeff
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