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SueinNC
02-08-2019, 10:19 AM
Hi all,

I paint in oils but usually do an acrylic wash to get rid of the white before blocking in. My teacher says there are reports of some acrylic paintings that are over 50 years old having delaminating problems. Does anyone have insight about this?

Thanks :wave:

Humbaba
02-08-2019, 10:35 AM
Hi,

There is always a risk with Acrylic/Oil formula, but I have not heard of acrylic delamination per se. You might try to read this document, I have no way to prove is 100% accurate though.

https://www.collectionscanada.gc.ca/obj/thesescanada/vol2/OKQ/TC-OKQ-1487.pdf

Richard P
02-08-2019, 10:51 AM
I recommend looking at this from GOLDEN:

https://www.justpaint.org/using-oils-with-acrylics/

contumacious
02-08-2019, 12:27 PM
On thing to consider is that the artist quality acrylics we have today are not the same stuff as 50 years ago. Also I think that more artists used acrylic house paint in their acrylic paintings 50 years ago than those who do today which might contribute to the rumored delamination.

stapeliad
02-08-2019, 12:31 PM
I think it is the paintings that were done when acrylic first came out that are having problems. Acrylic paint has been reformulated many times since. I would not worry about it.

contumacious
02-08-2019, 12:31 PM
I recommend looking at this from GOLDEN:

https://www.justpaint.org/using-oils-with-acrylics/

Some good reading there Richard. Thanks for the link.

Dcam
02-08-2019, 12:34 PM
It could also be that the painter did not add an isolation coat before painting in oils.
On a panel, I like Gac100, or matte medium. Clear gesso is good for more tooth.
All transparent.

contumacious
02-08-2019, 12:58 PM
It could also be that the painter did not add an isolation coat before painting in oils.
On a panel, I like Gac100, or matte medium. Clear gesso is good for more tooth.
All transparent.

A good point. Some acrylic paints can be very slippery, particularly when they completely obscure the canvas and are applied with a smooth and slick final surface such as with a knife or soft brush. Clear gesso or a matte medium significantly increases adhesion strength from my own experience and can act as an intermediary bonding layer between the oils and the slick acrylics.

sarahsands
02-08-2019, 02:17 PM
......You might try to read this document, I have no way to prove is 100% accurate though.

https://www.collectionscanada.gc.ca/obj/thesescanada/vol2/OKQ/TC-OKQ-1487.pdf

Yonah Maor's thesis is quite good and the work really seminal. However, people often misplace the emphasis of the study as being about the adhesion of oils to acrylics per se, when really the main conclusions and focus of the report were the adhesion problems caused by metal soaps, and zinc soaps in particular, that accumulate at the interface between the ground and subsequent paint layers. In fact, all the oil paints without zinc or other highly reactive pigments, like verdigris, adhered just fine. So really the main take away of Maor's thesis is not so much the dangers of acrylic grounds but rather the dangers of oil paints containing zinc oxide. Longer term, it certainly would be great to see this study repeated with oil grounds (both lead and titanium) as well as alkyd based ones, to see how that impacts the results. While we do have some of these tests started, it will, unfortunately, take several years before any meaningful results are available, and it would be even more ideal to have a third party, like a conservation department, carry out parallel research that might allow for a broader consensus and understanding.

MarcF
02-09-2019, 10:22 AM
If itís a concern, why paint with acrylic under oil in the first place?
Iíve been using oil based gesso as a primer, only because thatís the stuff I bought. I did not read the linked article, but the way you store things affect their longevity.
50 years sounds like too long a long timeframe to worry about it anyway. Even marble sculptures crumble eventually.