The titles of “Type 1” or “Type 2” are applied to adhesives used to glue wood. Type 1 is basically fully waterproof. Type 2 is water resistant. Both can also withstand a bit of heating without failure.
In either case, unless the glued wood product will be used outdoors or is subject to frequent wetting, either type will work well for furniture, cabinets, and similar. (Do not confuse these titles with the same nomenclature used for hardwood plywood. The plywood titles include further specifications about the interior veneer (inner ply) quality, as well as adhesive type.)
|
KNOWLEDGE CENTER Find more Wood Doctor at FDMCdigital.com Gene Wengert, aka The Wood Doctor, troubleshoots wood related problems, and explores lumber and veneer qualities and performance, species by species, in Wood Explorer, inside FDMC's Knowledge Center. |
|
So, how does a glue manufacturer rate their glue as Type 1 or Type 2? They make some birch plywood with three plies using their adhesive for gluing the veneers together. After curing the adhesive fully, for Type 1 testing, the sample of 1 x 3 inches is boiled in water for four hours, then dried at 145F for 20 hours, then boiled for four more hours and then cooled immediately and tested wet for bond strength using a shear test (trying to slide the veneers past each other).
Obviously, this boiling and heating test is much more severe than any glued wood product that we make will see in its life. But this test procedure is a valid way to compare one adhesive to another. Certainly a Type 1 adhesive can be used with confidence in almost any exposure. (Note that this is a test for the adhesive. All the procedures for making a suitable wood joint must also be followed to achieve high performance.) The shear strength required and the amount of wood failure versus glue failure is specified in the standard.
For Type 2, the sample used is 2 x 5 inches. The sample is soaked in water (not boiled) for four hours. Then the sample is dried at 120 F for 19 hours. Then the sample is soaked and dried again two more times, for a total of three cycles. To pass the test, the sample must not have delaminated. As before, this test is much more severe than almost any wood products will experience in use. However, it does allow for some “gut feeling” about the durability of the adhesive when exposed to water, such as with a water-based finish and a drying oven, or in use.
Technical Note: The correct names are ANSI/HPVA Type 1 or
ANSI/HPVA Type 2. Often we shorten them to “Type 1” and “Type 2.” The abbreviations in these long titles are referring to the sponsoring and development associations. This is a voluntary standard; a great option for avoiding a government standard, rule or regulation. Let’s hope that it is not abused. ANSI = American National Standards Institute and HPVA = Hardwood Plywood and Veneer Association.
Have something to say? Share your thoughts with us in the comments below.