MITRA Forum Question Details

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

Thanks for the reply, but I think it doesn't actually address the most important point.

Can we get a reply regarding the problem of UF degradation and conservation issues? I'm not in the US, so what US companies do with wood products doesn't matter to me - what I'd like to know is whether using UF-containing fiberboards will negatively affect my oils and acrylics as the glue outgasses and breaks down. Will the boards start coming apart? Will the acidity cause color degradation?

​Brian - Thanks for addressing the combination/issues concerning animal hide glues and UF. Regarding panels sold in the US and their regulations, these apply to any panels that are intended for sale to the US market as well. This means that we see this (nearly) as a complete industry change, regardless of country of production. 

Dana Brown

Ampersand Art Supply

​Thank you for clearing that up. Would you say that in a scenario where I can only choose between hardboard (wet-process, no UF) or UF-glued HDF/MDF, it's better to go with hardboard?