There are two forms of MDO plywood, a concrete form designed for industrial applications and a general form designed to be a paintable surface. The concrete form of MDO has a higher percentage of resin present in the overlay for increased durability, but it also contains a chemically reactive release agent to allow for easier separation from concrete molds. Of the two, the general MDO plywood would be best suited for painting. APA, MDO may not be a readily available product in most hardware stores, but it can usually be ordered in and picked up.
It is important to make note of how different manufacturers prepare an MDO panel by either pre-priming or specifying the need for appropriate priming before use. MDO plywood would be a suitable option for exterior muralists and panel painters working in either acrylics or oils.
Understanding a little bit about how a MDO panel is constructed, the type of resin used and how the plywood is classified can provide some insight into why it might be an appropriate wood panel option. Most wood panel products are manufactured using either a urea formaldehyde or a phenol formaldehyde adhesive. The difference between the two and why one would be used over another has a lot to do with urea formaldehyde being a water resistant adhesive and phenol formaldehyde being waterproof.
Manufacturing cost and emissions are also factors. APA, MDO plywood uses a phenol formaldehyde resin, also known as a phenolic resin, to adhere and saturate the overlay as well as bond the plywood veneer together. Phenolic resin is highly compatible with wood based products and will quickly penetrate into and wet-out cellulose fibers in its liquid state, then cross-link and harden when thermoset under heat and pressure.
The immediate benefits being high mechanical strength, chemical, moisture and heat resistant properties. Plenco, For a painter or muralist looking for a stable wood panel option, this increased resistance to moisture absorption correlates with a decrease in swelling when the panel is in conditions of high relative humidity.
This results in an overall increase in dimensional stability. Ebuka, Ezeh, Gimba, Mamza, The overlay itself will have a higher percentage of phenolic resin than the panel and will often be oriented with its strongest dimension perpendicular to the wood grain. This is designed to impart these structural benefits as well as improve resistance to surface checking or cracking. There are various exposure classifications of plywood, each related to the quality of the veneer and the performance of the bonding adhesive.
APA, This states that D-grade veneer is not permitted in exterior plywood and that an MDO panel should be composed of C-grade or higher veneer throughout with B-grade facings. This standard also requires that an exterior plywood be bonded using a waterproof adhesive such as a phenolic resin.
An overabundance of voids in the wood or a water resistant, not waterproof adhesive, could create opportunities for water to migrate through the panel, so these specifications are designed to provide improved structural resistance to moisture.
An exterior plywood is expected to be suitable for permanent exposure to weather and changing environmental conditions. APA, This classification does not relate to physical wear and tear or biological resistance to mold and mildew. The bond between the plywood and the overlay is also treated to the same standard as the bond strength between the layers of veneer. Before preparing a MDO panel for painting, if possible, it can be helpful to read the manufacturers specifications to see if the panel has been specially treated or pre-primed.
Typically, if pre-primed, manufacturers will apply a thermo-set acrylic to both the sides and working faces of a MDO panel, which will appear opaque and white. Make note of whether it is compatible with oil paints or latex waterborne paints when working in acrylics. If ever unsure, it is possible to do an adhesion test, which can be helpful if this information is not available or further assurances are required.
Always test if you are unsure. Testing for your Application. When using a MDO plywood outdoors that is unprimed, it should be appropriately edge sealed and primed on both sides with a high quality wood primer that is compatible with latex waterborne paints.
A light sanding is recommended prior to priming, to promote adhesion and reduce any potential evidence of wood grain. It is still possible for the grain of the wood to raise or the surface to become uneven and transfer through the overlay. This can also be a factor when displaying works or working in an environment with conditions of moisture or high humidity.
Here is are two Just Paint Article that goes in to more detail on preparing a panel for a life outdoors and a technical document on murals. Preparing a Panel for a Life Outdoors. Painting Exterior Murals.
The resin content in the overlay of a MDO panel should help to reduce the appearance of Support Induced Discoloration SID by reducing the amount of water absorbed into the substrate.
In our research we have not seen evidence of SID while using MDO plywood with acrylics; however, we cannot speak to the specifics of MDO from all manufacturers and we still recommend sizing as a precaution if there is concern. Testing is always recommended. When working with oil paints on unprimed MDO, we recommend 2 coats of Fluid Matte Medium or a similar sizing in order to block oil penetration into the substrate.
After allowing 24 hours dry time, this can then be primed with either an acrylic ground or an oil ground. For more detailed information on preparing a painting support for acrylics and oil paints, here is a link to our technical sheet.
Preparing a Painting Support. MDO plywood offers a lot of benefits as a painting substrate, it has a smooth surface treated to extend its life outdoors and provide enhanced durability.
MDO is also structurally classified as an exterior plywood, thereby specified to be suitable for both exterior and interior use. One thing to keep in mind about MDO; however, is that an overlay is typically used to upgrade panels that are of softwood construction. It is therefore possible for the surface of MDO to show some visual signs of reflectivity due to the varying densities of the underlying veneer.
APA, These panels may still telegraph repairs or show evidence of voids, which would need to be addressed if an artist were using MDO for exterior works.
If this is a concern, it is always possible to have higher grades of plywood or even marine grade plywood overlaid to gain its benefits. Since elevated levels of formaldehyde may lead to health conditions, regulations on emissions exist to limit the amount of exposure to it.
To better understand these concerns, it is important to know that formaldehyde is a volatile organic compound VOC , meaning it will vaporize or become a gas at room temperature.
APA, Wood panel products, which use phenol formaldehyde resins like MDO plywood, have been tested for emissions and have either met industrial standards or received exemptions from agencies such as U. If you have any questions or comments about this article or any other paint related topic, please feel free to contact our Materials Application Department at help goldenpaints.
Subscribe to the newsletter today! Uyility type retailers home depot etc typically dont bive a flying damn about creatives needs. Available with fiber surface on 1 side or both sides. All full and partial sheets are available through our online store. Click the TotalWoodStore link to see our selection available through our online store.
View Quote List. Out of stock due to material shortages MDO, also known as Signboard, is an exterior-grade plywood with a high-quality fiber surface saturated with phenolic resin solids. Are you searching for a strong durable panel that can be used inside or out that has a smooth paintable or routable surface?
Never heard of it or wondering what is MDO plywood? MDO is premium plywood with a durable weather and waterproof resin-impregnated overlay bonded to one or both sides. The smooth finish evenly accepts primer and paint, is routable, and can be used for anything from signboards to countertops and facia to wainscoting.
This guide will provide you with all you need to know about MDO plywood, so you can better make decisions for material choices for your projects. MDO is a specialty waterproof all-purpose plywood panel designed for exterior use. It can be used for all applications plywood or MDF commonly are used for, both inside and out. The plywood layers are defect-free and of uniform density allowing for cleaner and more detailed cutting, routing, shaping, and drilling.
The waterproof resin used to form the overlay or film makes the surface water and weatherproof and is thicker than a heavy block or butcher paper, and much more durable. The overlay forms a smooth surface that better accepts paint, stencils, veneers, and transfers than standard plywood. MDO plywood is manufactured using thin defect-free veneer layers of B and C-grade hardwoods or softwoods.
The layers are laid perpendicular to each other with a waterproof WBP phenolic CARB-approved glue layer between each veneer to bond and fuse them together as pressure and heat are applied. MDO panels have a tight, solid core for high strength, durability, and screw holding ability.
The waterproof bond resists humidity and precipitation for a superior surface life, while the smooth surface offers better paintability and finish adhesion. The panels resist temperature extremes, UV, moisture, swelling, mold, and insects. MDO plywood is easily cut and routed into letters or shapes for signage.
The smooth surface is easy to paint or apply vinyl or other medium prints or images for advertising, real estate or traffic signs, or other purposes.
The solid, defect-free layers allow for a clean chip and splinter-resistant finish too. As with all products, there are advantages and disadvantages. Some are more apparent when compared against other materials or uses.