MITRA Forum Question Details

Hi Koo

I have sent this question to the frame conservator on our board as he is acquainted with the behavior of various woods. I also forwarded it to George O. as he knows a great deal about traditional icon painting.

I do want to ask if you have any more specific info on what type of cedar? There appears to be many species and they may not all behave in the same manner. I have read that western red cedar works well for icon painting but have no corroboration of that.

While I am not an expert in wood, we did end up analyzing a very strange case of discoloration in a painting - especially impacting ultramarine blue - that we were able to trace, with some confidence, to the use of cedar stretcher bars which released acetic acid. See the following article for background in this:

https://jwoodscience.springeropen.com/track/pdf/10.1007/s10086-004-0654-y

Because of that experience, we have become very cautious about the use of cedar - and specifically western red cedar - if there is a potential for off-gassing to become concentrated. While cedar might be good for insect resistance, it remains a potential source of acetic acid, which is able to corrode some pigments. That said, I do not know enough to say if this has ever been traced to an issue in egg tempera, and the case we saw was a very particular one that might not be representative of the general risk in using this wood, so please take this as nothing more than sharing a case that surprised all of us.

Acetic acid would be an issue for the calcium carbonate or sulfate (analogous to Byne’s disease) making it a poor choice for a gesso or chalk ground.

Cedar is a softwood which comes from gymnosperm trees. Softwoods are generaly less dense than hardwoods. Medullary rays and tracheids transport water and produce sap. The sap produced by softwoods are known to exude from the wood and can present problems with staining and delaminating paint. Typically, icons were painted only on hardwoods. According to some icon experts, the best wood for icons is lime and cypress. It is worthwhile to note that these two types of wood, although ideal for use in iconography, are not used frequently, since cypress is almost inaccessible and lime is relatively expensive. Therefore, most icon boards are made from less expensive and more easily accessible wood. Poplar is an excellent choice, and it is possible to say that poplar in practice is not inferior to lime and can be successfully used as a material for icon boards.

Some West European manuscripts of the 17th century provide recipes for treating boards to protect them from insect damage. While these recipes greatly vary, most have in common one substance, garlic juice. Many old icon boards have a dark brown or black color on the back side. Investigations show that these panels were impregnated with substances similar to the recipes mentioned in the manuscripts, and also the brown coloration is due to its being impregnated with drying oil that affords a certain protection from insect attack and atmospheric moisture. Since the first century it was already known that the wood of some trees is not susceptible to insect attacks because of the presence of aromatic substances, which discourage insects. Such types of wood were given preference in panel paintings. It was much later that the back side of icons were frequently coated with oil paint, which besides giving a certain protection from insects, protected board from warping by preventing its one-sided drying. However, this method of protection from warping is not completely effective.

I am assuming that George is referring to European poplar and not the American variety known as tulip poplar. That species has no relation to the Old World variety. The closest wood we have to European poplar is cottonwood.

I received this from our resident frame conservator

In the past, artist’ would use discarded Cedar “Cigar” box lids to paint on, and using Cedar as a substrate for an Icon painting would be fine. It’s general characteristic is clear, straight grain and has a long history of being used in the furniture trades as well building and outdoor uses, fencing and shingles. There are many species of Cedar from around the world and most if not all are stable, some unique characteristics, aromatic as well some having a natural decay resistant properties. The only problem is the size of the Icon to be made and the proper support required and this would depend on the panels thickness as to possible bowing, as one of the problems. Another problem is that this wood is very soft and that distinction “soft” is relevant, any sharp hit the panel might receive over time would be magnified as opposed to using a harder wood. Throughout history Artist’ would use regional native woods but today one can order or travel to a local Lumber Yard, kiln dried, whatever they would like. Oak, Mahogany and even Poplar have been used throughout history as the standard for panel painting, but softwoods such as Pine, Lime, Fir and Fruitwoods all have been used as well, all have their own attributes as well negative physical properties. The choice of Cedar is fine, it is the artist’ preparation of the panel, that is another hurdle.

Martin Kotler

Frame Conservator

Smithsonian American Art Museum