Saturday, March 17, 2012

About Varnish


 It was the French Impressionists who made the varnishing of paintings optional. Some of them liked the flat, matte look of dried oil paint. Today, I personally know one high-end painter who doesn't varnish his paintings.

The problem with not varnishing paintings is twofold. First, not all colors dry to a matte finish. The amount of gloss depends on oil content, how much thinner or medium was used, and also on the absorbency of the ground. An uneven gloss can detract from the beauty of an otherwise skillful painting. Second, a painting without varnish is much more difficult to clean. Paintings in the home are routinely exposed to smoke, airborne kitchen grease, pollen and other particulates that will dull and darken color over many years. With varnish, it's a simple matter of the conservator using some solvent and a light touch to remove the varnish and the accumulated grime.

All that said, painters look at varnishing as an unwelcome task. Mostly, it has to do with timing. An oil painting needs to dry for at least six months before applying a final varnish. Even though the painting might feel dry, oil dries not by evaporation but by oxidation. It doesn't "dry" so much as it "cures." Thicker passages of paint especially may still be soft and contain unpolymerized oil. A final varnish will seal the paint, keeping away the oxygen that the paint so desperately needs for curing.

But there's an easy way out - retouch varnish. I know many painters who apply a coat of retouch varnish but never bother with a final varnish. Retouch varnish can be applied at any point, since it's often used to revitalize dried, dull color during the painting process allowing for colors to be more accurately matched. When I'm done with a painting, I usually give it a couple of weeks and then apply a light coat of retouch varnish. The retouch varnish brings dull color back to life and also evens out the gloss. Typically, this is all the painting needs. Sometimes retouch varnish will seem to disappear over time, making parts of the painting look uneven again. But I don't just spray on more retouch; retouch is just a dilute version of final varnish, and multiple coats of it will seal the painting just like the final varnish. If the painting has sold, I offer to take the painting back from the buyer and varnish it.

I use either a spray varnish or a bottle with a brush. Spray varnishes tend to get clogged nozzles, leading to varnish blobs. I always do a test spray first to make sure I know how the nozzle will work. I prefer a brush, but sometimes while leaning over the painting, I end up getting a dog hair or two in the varnish. If I'm quick, I can pick them out without damaging the varnish. When I'm done, I always make a note on the back of the painting with the type of varnish used and the date.  As a side note, make sure you varnish on days of low humidity.  I don't know about acrylic or resin varnishes, but damar will "fog" if applied on a wet day.

By the way, if you like a matte finish to your paintings, you can get a final varnish that gives a matte finish.  You can have the flat, dull look of dried oil paint and still have the protection!

Above are some of the varnishes I have in my studio today.

13 comments:

Jaimehowardart said...

Thanks for the information about varnish. I've seen paintings in galleries with distracting patches of shiny paint. Sometimes it makes the image difficult to see.
I have used Gamvar by Gamblin on my paintings, but I didn't know that retouch varnish was a sort of substitute.

Michael Chesley Johnson said...

Hi Jaime - You can also use Gamvar as a retouch varnish. Here's what Gamblin says: Gamvar is not premixed like most varnishes. Conservation scientists have advised Robert to formulate Gamvar as a component system because all varnishes should be mixed and used immediately. Gamvar may be used as a retouch varnish (1 part Gamvar to 5 parts OMS).

mary pyche said...

It might be helpful to mention that there are semi-gloss finishes as well for those who don't care for the high gloss look.

Michael Chesley Johnson said...

I do mention the matte finish varnishes but, yes, there is also semi-gloss.

Goldenthreads777 said...

Thanks Michael for the information. It's nice to have it concise and brief. I've been getting dribs and drabs from a variety of sources, but your explanation is more helpful. Thanks again.

CCAdamec said...

Thank you so much for the information about varnishes. I have heard a variety of different methods regarding varnishing, but your explanation provides good methodology. Thanks!

Peggy said...

Michael do you have an opinion on Liquin Light Gel for evening out the 'shine' or gloss? I stand to be corrected on this, but a friend that took a Scott Christensen workshop told me that's what he uses.

Michael Chesley Johnson said...

Not really sure, Peggy, since I don't use it. However, W&N states that Liquin products should not be used as a varnish or final coat:
http://www.winsornewton.com/products/oils-solvents-mediums-varnishes/oil-colour--oils-solvents-mediums-varnishes/mediums/liquin-light-gel-medium/

Michael Chesley Johnson said...

And more on Liquin from W&N:
7. Can Liquin be used as a varnish or final coat?

It is definitely not advisable to use Liquin as final layer to a painting based on the reasons below:

- Unlike other modern picture varnishes, when dry Liquin is not soluble in normal paint solvents. Therefore when the picture surface becomes discoloured by ingrained dirt from the atmosphere, it cannot be either completely cleaned or removed and the picture re-varnished.

- Although Liquin has much better resistance to yellowing than linseed oil, it will discolour more than acrylic varnishes.

- Liquin will seal the surface of the painting and prevent the drying of underlying paint layers. This is similar to Artists' Painting Medium. All produce a continuous film which excludes oxygen and delays the drying process - hence the recommendation to wait at least six months before varnishing. It is therefore advisable to use one of the Winsor & Newton specifically formulated varnishes

Michael Chesley Johnson said...

A reader writes: My understanding is that cold wax medium can be applied to a painting before its paint has thoroughly polymerized; that the oils beneath can keep on curing beneath the wax medium. I see you also have it among your varnishes; do you use it when a painting may not be entirely cured?

I checked with Product Manager (and painter!) Scott Gellatly at Gamblin, since I haven't tried this myself. Here's his response: Yes, the painting will still continue to dry underneath the thin layer of CWM. We recommend allowing the painting to dry long enough until the paint layers are not disturbed by the application of the wax medium (by gently rubbing the wax on with a cloth). Generally, this is when paint layers are touch dry, but any thick impasto should be dry throughout.

Daniela said...

I bought your book "Through a Painters Brush - A Year on Campobello Island" about 2 months ago but have not had time before to really spend time with it. I disagree that it is not an instruction manual, it is a delightful book full of choice morsels of sound information. It is also a "feel good" book (I tell people if asked, not to buy an instructional art book if you feel no affinity with it and if the art work in it is mediocre). I admit I love the brush stroke textures and therefore the oils more so than the pastel paintings. And I love your dog!

Michael Chesley Johnson said...

Why, thank you, Daniela!

Phil Kendall said...

always enjoy reading your blog when highlighted on Canavoo...
The next time you revamp your website perhaps go for a paler shade to improve its readability?

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