To continue our series about Painting on Panel, I've pulled together information on the differences between HDF or High Density Fiberboard and MDF, Medium Density Fiberboard. I realize these posts are rather on the technical side, so please post questions if you have them. We are here to help you make good choices for the longevity and beauty of your art.
Hardboard is most commonly associated with Masonite, as this was the first “brand” of hardboard invented by William Mason in 1942. Hardboard is often confused with high density fiberboard (HDF) or medium density fiberboard (MDF). Producers of these different panels use reconstituted wood (saw dust and chips) and use different methods for manufacturing that in turn produce panels that have different characteristics in terms of density and internal bond strength. One of the most significant differences between Hardboard and fiberboard panels (both MDF and HDF) is the method of manufacturing. MDF and HDF panels use a dry process method and use synthetic binders or formaldehyde based agents for binding the wood fibers. In comparison, Hardboard uses a wet/dry process method that relies on the natural binders within the wood to cement the fibers together and make the wood solid.
The wet/dry process used to manufacture Hardboard has several advantages. The wet process method produces a smooth-one-side (S1S) panel, while the wet-dry process produces a smooth-two-side panel (S2S). Both processes explode the wood particles using steam pressure, and float them in a large vat of water, which pulls out many of the naturally acidic agents within the wood. The wood fibers are then randomly aligned parallel to the surface, and using heat and pressure, are made into a solid core panel. Ampersand’s Hardboard also has an added overlay of a neutral aspen fiber layer. This process allows a very uniform and very strong panel, making it one of the best substrates for painting, laminating, and construction. While still a relatively light-weight panel, Hardboard has a significantly higher density compared to MDF panels with a much higher tensile strength and internal bond than MDF and most HDF panels.
As mentioned earlier, Ampersand’s Hardbord is made using the natural binders in the wood. No added formaldehydes (NAUF) are used in Ampersand’s Hardbord, providing a virtually VOC free panel.
What you need to know:
• Hardboard panels are probably the best value on the market for artists today.
• Tempered panels produced within the U.S. no longer have the topical oil content they once had. However, very small amounts of tempering oil continues to be added to the integral fibers. Linseed oil is the natural agricultural oil use in the manufacture of hardboard.
• Hardboard is more dense than MDF and HDF, making it less prone to warping while still lightweight.
• Hardboard is a very uniform and stable surface without a grain, making it easier and faster to prime.
• Only natural binders used.
• Provides a pressed steam ironed surface to create a smooth gessoed panel.
• Larger panels can become heavier.
• Flexibility of the surface requires thicker hardboard to be used for larger paintings.
Medium Density Fiberboards (MDF) and High Density Fiberboards (HDF) are engineered panels that are made through a dry process that completely breaks down the particles of wood and reconstitutes them into a new panel using heat, pressure and a binder. One of the most common binders used in their manufacture is urea formaldehyde, leading to potential problems with out-gassing. MDF typically has a density of 600-800 kg/m³, as compared to hardboard, which has a density nearly double that of MDF (1,450 kg/m³). HDF panels come closer to the densities of hardboard but are still normally 10 lb/ft³ lower in density than hardboard, making them more porous and more prone to warping, especially in an 1/8” thin version. More layers of sealing and gesso are required to eliminate the fiber raising that happens with MDF and most HDF’s on the market. MDF and HDF technology is rapidly changing and we will see better MDF being produced without formaldehyde as the binder and MDF that is much more dense and less prone to warping in the future.
What you need to know:
• If using MDF/HDF, make sure to seal the surface with several coats of Gesso and a good acrylic seal like GAC
• Even with cradling, there is a high potential for these panels to warp over time
• MDF is not a high-density board. Fibers are very porous, and have a tendency to swell when painted, leaving a very uneven surface.
• Lightweight and inexpensive.
• Original organic structure of wood completely broken down to allow for consistent specifications.
• Future potential – could be a good panel in the future as technology improves density and binding material used.
• Not a dense panel – high tendency for warping in thinner versions.
• Porous, therefore not easily primed.
• Forrmaldehyde based resins primarily used for binders.
• High acidic content.
• Fibers swell when gessoed.
All things Ampersand,
Artist & Social Media Specialist
Ampersand Art Supply
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