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More Information about HDU

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  What is it? -

"HDU" is short for high-density urethane foam. Unlike other foam with which you may have experience, it consists of much more solid and much less air. Using urethane as a base means that it is impervious to all petroleum-based solvents. Even in it's "raw" state, it is completely waterproof and unaffected by climatic changes. Almost every sign pictured on this website is made of HDU.

  A material engineered expressly for the sign industry -
Years ago, enterprising chemists saw the need for a durable, predictable material for use in three-dimensional signs. They saw many problems with wood and sought to create a superior replacement. They discovered urethane foam, and then worked to refine and improve it. Today, "Sign-Foam" and "Precision Board" are brand names for high-density urethane foam manufactured to precise standards expressly for the sign industry.
  Worked with standard woodworking tools
HDU comes in various-size sheets (we work with 4' x 8') and various thicknesses. We stock, usually, 1" & 1.5" thick and laminate when thicker is required. Urethane glue creates a bond as strong as the material itself. It also comes in various densities. 15lb was originally engineered as a replacement to top-grade redwood, and that's what we use.
   No warping or splitting .... ever
All wood comes from the mill as various size boards. They have to be laminated together in order to build larger blanks. If not done properly, every time, problems can develop along the joints, especially in harsh exterior use. HDU, in 4' x 8' sheets, eliminates this.
Wood, being a natural material, varies from board to board. Unless boards are very carefully matched, every time, these differences can cause warping and other problems. Again, especially in harsh exterior use.
HDU is an engineered material. Consistent quality is guaranteed
   Impervious to rot, painted or not.
  Anywhere most types of wood go thru wet & dry cycles with fresh water, wood rot is a problem. Only all-heart* redwood or cedar have a natural resistance**. A fungus develops inside the wood which turns it into crumbling mulch. This includes the finest hardwoods; certainly plywood. The defense is regular maintenance of the wood finish, to ensure that it remains completely sealed. As soon as the seal is compromised, and moisture gets in, rot begins. Most people are not interested in signs that require this level of commitment.
*cedar, especially, can be "all-heart" with the darker color, or light "sap wood"; often on the same board. "Sap wood" has no resistance to rot. ** teak, also
  Better than cedar?
Much, but not all, cedar has a natural resistance to rot. We've worked with it since 1978. Cedar is great when a natural, rustic look is called for. It's perfect for routed signs; but has never been the first choice for sandblasting; mainly because there's not much difference between hard and soft parts of the grain.
It's also not a good choice for fully-painted signs, or designs featuring detailed painting. Cedar is a soft, porous wood and difficult to seal up. It swells and shrinks with changes in the weather, making it difficult for paint to adhere well over the long term, especially in harsh exterior use.
  Paint finishes stay looking new years longer
All our signs, as delivered, are designed for extended exterior use; maintenance free, no matter what the climate.
HDU is a "closed cell" foam. Water cannot penetrate. It's also stable over a very wide range of temperatures. This makes for a much more stable base. It's the constant shrinking and swelling, and changes in moisture content, that causes premature chalking, fading and even peeling of paint finishes on wood surfaces.
  Woodsigns.com??
For 20 years, I worked exclusively with cedar and redwood. Top-grade redwood became increasingly scarce, while "rustic" and "natural" styles faded in favor of more colors and artistic painting. HDU offers the look of sandblasted wood, with greatly increased maintenance-free exterior durability, no matter how detailed the painting. I'm confident, if you have us build a sandblasted HDU sign, you'll be pleased with the results.    John Heimberger

We hope that answers your questions about HDU, but don't run off. There are links below to other parts of the website.

Start - Sandblasted Res.- Routed Res.- Commercial - Sandblasted vs. Routed - How they're Made - About Us