I have recently read that the outgassing of formaldehyde from urea-formaldehyde used to manufacture HDF and MDF is a problem when it comes to conservation, since it can influence the acidity of both the work and the environment, leading to possible degradation of the artwork. I also read (Getty’s “Facing Challenges of Panel Paintings Conservation”, part 3 by Paul van Duin) that urea-formaldehyde itself degrades over time and the author estimates its longevity (when protected from light) to be a couple of decades. In light of this, I was wondering if hardboard (wet process board) wouldn’t be a better choice, since it doesn’t contain UF?
On the other hand, I used to coat the panels I paint on with a water solution of PVA with a pH of 6-7 (according to manufacturer), and I read that PVA can be a source of acetic acid, but I’m not sure if this is relevant.
Thank you for the reply.
Would you say that a hardboard with no urea-formaldehyde is superior to HDF and/or MDF with urea-formaldehyde?
Two related questions/comments:
– I belive the formaldehyde issue is relevant to plywood glues as well, yes?
– I’ve read that many (most?) engineered wood products now meet “CARB” (California Air Resources Board’s) stringent emission levels, and to ask for the CARB seal of approval when buying fiberboards. The EPA is in the process of applying these standards nationally, (see: https://www.epa.gov/formaldehyde/formaldehyde-emission-standards-composite-wood-products), although in the current political climate I’m not sure what will happen. Regardless, I think the industry is trying to get on board with CARB standards. Anyone know if that’s accurate?
Koo
There are several points and questions made in the string of posts above and we will try to address each one and comment. We will mostly focus on the urea formaldehyde (UF) concern and outgassing. However, we agree with the comment above that the deterioration of PVA size is not of major concern due to its non-acidic nature and flexible bond.
Urea Formaldehyde:
With regard to UF still present in composite panels (such as MDF, HDF, Hardboards) and hardwood plywoods, it is correct that the EPA will require manufacturers of composite panels and hardwood plywood to be CARB compliant (adhering to California standards) over the next few years. (unless of course the EPA policy changes). Many if not most manufacturers of these products are moving in this direction voluntarily. For example, all composite panels and products made from composite panels coming into the US from abroad must be CARB compliant, meaning that they have to meet the standard that the California Air Resources Board has set for UF in composite panels. The following link provides more information on the standard: https://www.arb.ca.gov/toxics/compwood/retailersfacts.pdf
There have also been developments of low-emitting and no added urea formaldehyde (NAUF or NAF) panels on the market and are available for purchase. US made hardboard does not contain UF and therefore is one of the only composite panels that is exempt from CARB regulations. This is only one of the several reasons we choose to use the hardboard as the base substrate for our panels.
MDF & Hardboard:
In general, the bigger issues with MDF (medium density fiber boards) and HDF (high density fiber boards) have more to do with their density and dry-process construction. When the density of a wooden panel support increases, there are improvements in its stiffness, internal bond strength, and resistance to moisture absorption. Thinner MDF panels are more susceptible to water absorption and more prone to warping than HDF, for example. While a thicker MDF panel may help to reduce its tendency for warping, it can still have issues due to excessive moisture absorption. This moisture includes issues such as fiber raising when applying priming coats. A denser panel in comparison will accept a smoother coating of primer, reducing the number of gesso layers needed to properly prepare a panel with a smooth painting ground.
Hardboard and high-density fiber boards for example have a higher density and will absorb less moisture and be less prone to warping or fiber raising. Moreover wet process manufactured hardboards that are tempered are even more resistant to moisture absorption and are considered one of the better substrates for commercial finishes.
For more information on substrate comparison for wood panels, you may want to refer to an article Ampersand wrote for Golden’s Just Paint newsletter. That article, while a few years old, compared various wooden panel support options and addressed advantages and disadvantages of each. These comparisons were made pertaining to density, internal bond (the force that it takes to pull a material apart), modulus of rupture (the maximum breaking strength of a board), and moisture absorption. http://www.justpaint.org/understanding-wood-supports-for-art-a-brief-history/
This article helps to illustrate the benefits of one panel selection over another, based on its overall stability and resistance to moisture and movement. It may be worthwhile reading for more detail on these differences.
Dana Brown
Ampersand Art Supply
Hi
Good points and questions. There is evidence of the deterioration of urea-formaldehyde adhesives which release harmful vapors.
First, you can purchase zero formaldehyde MDF. This quality is used for museum displays where issues of off gassing are paramount. Hardboards can also be purchased with no formaldehyde component. I find neither MDF nor hardboard perfect due to other physical properties but that is another issue. I do not believe that the deterioration of PVA is a major concern but if you want to be extra careful, use a diluted high quality acrylic dispersion or even an acrylic solution (eg B-72 in acetone/ethanol) as a size. Others may have additional thoughts on this matter.
At this point we have an inquiry into a couple of our moderators who are more knowledgable about these products….so hang tight. There will be a detailed response come Monday.
Koo, you are correct as to the relevence to plywood as well. We hope to hear from someone very well versed in these issues rather than postulating ourselves.
The off gassing of UF glues is known to tan and embrittle animal glues like those sometimes used as a size or incorporated into genuine gesso or chalk glue grounds.
There is also mention in the literature that it can also contribute to the degradation of some pigments. This one of the reasons why materials containing it are avoided in museum displays. I do not believe that the concern is necessarily about the structural failure that you are worried about.
It is difficult to know if your use of such materials would be a major problem but they should be avoided if possible. If you continue to use these substrates avoid the use of animal glues and make sure that your panel is well sized/sealed before applying your ground and paint layers
In this scenario, I do believe that the zero-formaldehyde wet-process hardboard is the better option, especially if it is braced for rigidity.
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