Re: Acrylic over oil 398 by Patrick on 03/23/01 at 12:08 PM
Re: Acrylic over oil

In Reply to: Re: Acrylic over oil posted by rob howard on 03/22/01 at 6:49 PM:

: >>>Acrylics do not adhere well to oil films.<<<

: Despite what you may have read, actual tests prove the reverse. Another thing for you to read (after making the tests) is what Ralph Mayer has to say on the subject.

: Oil primers are highly regarded in industrial applications of water-soluble acrylic paints whereas oil over acrylics causes problems in outdoor applications (which is just a speeded up version of the destruction that takes centuries to accomplish with artistic applications).

: Make a few tests. Paint some acrylic over a CLEAN and DRY oil surface. Allow the acrylic a week to cure and then try to remove it. It's not as easy as the sales lit says.

: Understand that the sales lit is written by lawyers to cover their corporate arses when some blockhead slathers acrylic over freshly painted oils.

I have to admit I have heard nothing about this new way of thinking! On one hand, this will have me doing some new research, but on the other, I won't be changing my habits soon until I find some compelling evidence. And maybe even not then - I'm not much of a fan of the look of acrylics anyway! :)

Just putting paint on and trying to take it off a few weeks later is much different than letting it sit for a few years, of course. Since up until now most research has shown the opposite of what you are saying, as well as every book on the subject I've ever read (many!), I think I'd like to let it shake out a bit before taking any chances.

One observation - oil gesso is very different that oil paint. While acrylic "gesso" primer is essentially the same as acrylic paint, oil primer is really a gesso - a glue sizing made with glue, water and chalk or other whitener. This would be a lot different than painting over oil paint, wouldn't it? Also, an oil primer made for house painting sounds very different from the sort of oil primer I would find in the art store, but I don't know. I'd like to find out.

I would also like to reiterate one of the important points of this problem. Before putting any fast-drying layer on top of the oils, they should be completely dry. This is different from the common idea of "dry". Oils can be dry and seemingly hard to the touch, but are still undergoing a chemical transformation. If the layer on top is totally dry and doesn't let air into the layer underneath, the lower layer will crack. This may take several years to occur, but it will happen. The "fat over lean" rule helps avoid this - the "fat" (oily) layer takes longer to dry.

A good, if exaggerated, example of this is to look at Norman Rockwell's original paintings. A lot of them are cracking horribly, due to his habit of putting on fast-drying retouch varnish between layers. Of course, he did this because he was working on a deadline and had to get the art out to be printed, but most of us aren't working under those constraints.


Follow Ups:


Post a Followup 380,385,388,397,398"> Patrick"> megaflowpm_aol.comRe: Acrylic over oil_03/23/01 at 12:08 PM"> "Re: Acrylic over oil"
>>>Acrylics do not adhere well to oil films.<<< Despite what you may have read, actual tests prove the reverse. Another thing for you to read (after making the tests) is what Ralph Mayer has to say on the subject. Oil primers are highly regarded in industrial applications of water-soluble acrylic paints whereas oil over acrylics causes problems in outdoor applications (which is just a speeded up version of the destruction that takes centuries to accomplish with artistic applications). Make a few tests. Paint some acrylic over a CLEAN and DRY oil surface. Allow the acrylic a week to cure and then try to remove it. It's not as easy as the sales lit says. Understand that the sales lit is written by lawyers to cover their corporate arses when some blockhead slathers acrylic over freshly painted oils. : I have to admit I have heard nothing about this new way of thinking! On one hand, this will have me doing some new research, but on the other, I won't be changing my habits soon until I find some compelling evidence. And maybe even not then - I'm not much of a fan of the look of acrylics anyway! :) : Just putting paint on and trying to take it off a few weeks later is much different than letting it sit for a few years, of course. Since up until now most research has shown the opposite of what you are saying, as well as every book on the subject I've ever read (many!), I think I'd like to let it shake out a bit before taking any chances. : One observation - oil gesso is very different that oil paint. While acrylic "gesso" primer is essentially the same as acrylic paint, oil primer is really a gesso - a glue sizing made with glue, water and chalk or other whitener. This would be a lot different than painting over oil paint, wouldn't it? Also, an oil primer made for house painting sounds very different from the sort of oil primer I would find in the art store, but I don't know. I'd like to find out. : I would also like to reiterate one of the important points of this problem. Before putting any fast-drying layer on top of the oils, they should be completely dry. This is different from the common idea of "dry". Oils can be dry and seemingly hard to the touch, but are still undergoing a chemical transformation. If the layer on top is totally dry and doesn't let air into the layer underneath, the lower layer will crack. This may take several years to occur, but it will happen. The "fat over lean" rule helps avoid this - the "fat" (oily) layer takes longer to dry. : A good, if exaggerated, example of this is to look at Norman Rockwell's original paintings. A lot of them are cracking horribly, due to his habit of putting on fast-drying retouch varnish between layers. Of course, he did this because he was working on a deadline and had to get the art out to be printed, but most of us aren't working under those constraints.

 
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