Best support option to protect against high humidity?
 

Hi

I have a portrait commission destined for a family currently living in Burma (Myanmar). The high humidity there is causing my client and I concern regarding potential damage (warping particularly comes to mind) to the support. They will also be bringing the painting back to a country with lower humidity in a few years time so it needs to stand up to this change.

Has anyone any experience/advice in this instance? Especially regarding the best way to construct a support (I often use canvas or linen stretched onto a 5mm piece of marine ply - would bracing this across the back be sufficient?)

The painting will be relatively small - only approx 20 x 20 inches, and as I say oil on canvas or linen.

Thanks in advance.

Mary Jane

Opinions will no doubt abound. My personal bias is paintings under 3 sq. feet are best executed on panels; larger than that, on stretched fabrics.

Extreme changes in humidity (how extreme?) will be problematic in this case, regardless of what materials are employed. On the other hand, you may be overestimating the intensity of this "shock".

High-quality plywood would be my choice in this instance, regardless of how the painting ground is prepared. An oil ground on the wooden panel would be "best" in my opinion, with the panel prepped both sides. It is well to consider the fact that it is impossible to "seal" any wooden item from changes in ambient humidity, even with all surfaces coated. In fact, it is often inadvisable to attempt it.

For my part, it would be better to use plywood 1/2" to 5/8" in thickness rather than thin 5mm (about 1/4"?) stuff. Reinforcing a panel with a cradle is a task demanding a very high level of wood-working skill. The cradle bars need to be fitted very accurately where they cross and interlock, and should not be glued to the panel along their entire length, as this will inevitably "telegraph" to the surface of a thin panel face. Suitable cradles are glued to the panel edges at the tips of the bars, and "float".

A good alternative to a wooden panel with an oil ground would be 1/16" thick ABS (acrylonitrile-butadiene-styrene) sheet laminated to suitable plywood. In the event severe changes in humidity cause the plywood to fail, an ABS veneer could be re-lined with another panel quite easily.

While there are concerns of high humidity, and its effects on the painting, it's really not a major problem as long as you adhere to two things:

• Getting the painting to dry adequately before shipping

• Avoid storage of painting in enclosed environment before shipping

These points serve as reminder to discourage mold bacteria from growing on it, before we even ship it to the location.
However, if you're still worried about problems with humidity, you may consider talking them into sending the painting rolled up (and in vacuum pack), and your customers can have them stretched using wood that is suitable for their environment. Hope you find these tips helpful

Thanks for your helpful points Richard and Marcus.

Richard, my feeling was for a thicker high quality ply panel but will also pursue ABS (I have not used it personally)

My canvas maker just suggested MDF but I'm never keen on it personally, he also reminded me how important it will be to have the painting carried in hand luggage - he having just seen a canvas of his warped horrendously in the hold on its way to Portugal recently...

The humidity can range from 20% to over 85% (which - gasp - it is currently!)

Marcus, I shall do my best to get it thoroughly dry, actually thats a bit of a worry though as that may be very hard indeed - the family are coming back to the UK at Christmas to collect it!! :-/

This may sound silly but, Has anyone thought of vacuum packing? Do you think that mite work?

Hi Mary, i meant to say the painting needs to be dried with the lowest moisture level as possible, when i suggested drying adequately. What we're concerned about is the explosion of mold bacteria that may sit with the painting dormantly in the temperate region and into Asia.

It's the same idea as having yourself in an air-conditioned environment and moving into the hot summer sun immediately - you'll find yourself drenched with moisture! That's what i want to say.

Just a couple more thoughts. MDF would be the worst possible choice for panel material in my opinion, because being compounded of wood flour, glue binders of indeterminate composition, and floor-sweepings, it is neither structural nor does it resist the absorption of ambient humidity even as well as solid wood.

Vacuum packing would be a solution if the painting were never to be exposed to a climate other than the one in which it was painted. The slower the change to different ambient conditions, the better - hence, a "slow boat to China" would be theoretically better than air freight!

Curiously, ambient humiditiy does not affect the "drying" of oil paints and the varnishes and solvents normally used with it. Oxidation is the process which "dries" paint, and while high humidity may affect the rate which solvents and volatiles "off-gas" in the process, oftimes, paint will actually "cure" better in the presence of some moisture than in a bone-dry climate such as in the Arizona desert.

Finally, one of the properties of paints which has enabled such coatings to preserve wood and other materials, is the fact that the vehicles employed are innately pretty good fungicides/bactericides. A relatively fresh painting will be unlikely to "grow" stuff . . . terpenes and other volatiles would prevent that. To this end, it would be advisable to apply a coating of an oil ground to the back of any painting support. The open backside of a canvas sized with hide glue would present an ideal medium for growing "things", however!

ABS panels would be a good bet. These plastic panels are dimensionally stable and fairly impervious to moisture. Do a Forum search for ABS panels and you will find that a lot of noted portrait artists use them with great success.

Hi Mary,

I've been doing a bit of hunting around myself recently on options for supports, and came across this page about Dibond which may interest you:

http://www.welshartsarchive.org.uk/a...els-burton.htm

Thank you all very much. I've researched the very helpful points raised further and have to say Paul, I'm really impressed with the Dibond you mention... I've just spoken to them and they were extremely helpful despite my very small requirements.

I was sold before they explained that The Tate and many other galleries use Dibond as a support for artwork or for any number of other uses.

I eagerly await my sample!

MaryJane.

Good news, decent service is hard to find. You're way ahead of me, I haven't even called them yet. Would be very interested to hear what you make of it.

Hi Mary,
I also have problems with high humidity, mold, etc with my work. Mold loves fresh oil paint, it seems. Some years ago I painted quite a few oil on ply pieces. Sealed the support, dried the paint, even varnished the pieces. Finally had to discard them because the mold penetrated throughout.
I now paint only on stretched canvases and mostly don't have any problems.
The best recommendation you can make to your clients is that they hang the piece on an internal wall.
I have a beautiful watercolour under glass which some genius of a framer bonded to craftwood. I had no problems with it until we moved house and it was hung on a wall near a window. Every year I get a furry mold growth on it, as soon as the wet season starts, and I have major dramas having to take it out of the frame, sterilizing the glass, vacuuming the painting, drying it, etc etc..
I have recently found a varnish which is completely invisible, which is especially designed to retard mold growth on anything. I am about to experiment on my watercolour.
cheers Margaret

Hi Paul

I'm mid-way through my first batch of work on the linen stretched Dibond - I opted to use acrylic gesso as the adhesive as, while the BEVA your link referred to sounds a really excellent option, I could only find it available in the US and due to a very tight deadline didnt have the time to wait for an order (nor the inclination to order the 27 x 5 ft rolls it seem to come in!!) Hopefully at some future point it will be very good to try it though.

I tested a number of methods of stretching linen onto it and in one instance noticed that on applying an iron (as the BEVA instructions would require) you may need to be reasonably careful, I seem to have managed to get a slight divet in the metal sheet which I could only put down to a reaction to too much localised heat from the iron.

I can't say enough that the service I got from the Robert Horne Group who supplied me with the Dibond was fantastic from start to finish. I phoned through my order and it was with me, perfectly cut down to my requirements within 24 hours. If only every company I deal with was like that!;-)

Margaret - sorry for such a delayed response - thanks for your suggestions. What a terrible pain that mold must have been!

Once the mold spores are settled into something I know they are nearly impossible to permanently remove and it makes much sense to that a stretched canvas will fair better as it should remain inherently dryer as good fresh air gets to it more easily - very likely the sealed panel and perhaps unfortunately even the craftwood your watercolour is bonded too may be harbouring those darn mold spores and off they bloom each wet season!

I'd love to hear if your mold retardent varnish helps - hope so! There is some theory that ozone kills mold so failing that you could give it a blast?! Not sure how you go about that though!!!

Best wishes
Mary Jane