What is the difference between HDO and MDO plywood?
HDO carries a dense phenolic resin overlay that casts a glossy, closed concrete face and stands up to high pour counts. In formwork searches MDO usually means a matte cast face, and buyers often search for MatteFace as MDO formwork plywood; our product for that finish is MatteFace Plywood (MTF), made for formwork only. The kraft-paper MDO described by APA is a different sheet, built as a paint base for signs and exterior panels. Choose by the finish the drawing calls for and the number of pours you need.
Is HDO or MDO better for concrete forms?
For high-rotation gang forms or a glossy exposed face, HDO is usually the better start, because HDO Standard and HDO Premium are rated for up to 20 reuses with good site care. When the architect wants a matte face, MatteFace Plywood is the sheet buyers often search for as MDO formwork plywood, and its single-face panels are rated for up to 15 reuses. Put the finish and the pour count on the RFQ so the quote matches the job rather than the cheapest overlay.
How many times can HDO plywood be reused?
HDO Basic is rated for up to 10 reuses, while HDO Standard, HDO Premium and HDO Premium HD are rated for up to 20. Those figures are maximums, and crews reach them when cut edges stay sealed and release agent goes on thin before every pour. Panels dropped on their corners or stored flat on wet ground fall well short.
Can you paint MDO plywood?
Kraft-paper MDO, the APA overlay class, is made as a paint base and is common on signs and exterior panels. MatteFace Plywood is a matte phenolic forming film for concrete work, so it is not a paint-grade sheet. If the job is a pour, specify MatteFace or HDO by the finish you need; if it is a sign, kraft-paper MDO is the product to look for.
Does a denser overlay mean the panel is phenolic Class 3?
No, because the overlay and the glue in the core are separate parts of the specification. At Vinawood, Pro Form, Pro Form Lite, HDO Standard and HDO Premium are bonded with phenolic glue to EN 636-3 (Class 3), while HDO Basic is Class 2. Form Extra uses a higher-melamine MUF glue to EN 636-2 and is not Class 3, even though its face film is phenolic. Write the overlay and the bond class as two separate lines on the RFQ.
What is telegraphing on overlaid plywood, and does it show on concrete?
Telegraphing is when the grain or patched spots in the veneer under an overlay show through the face. On a sign it spoils the paint, but on a form it can print into the concrete, which matters most on exposed architectural walls. Before ordering for visible concrete, ask how the core is patched and sanded before the overlay goes on, and check a sample sheet under low, raking light. A face that looks even across the sheet will usually cast even.
