Four more adhesives you should know about
In our tests, we found that white glue bonds with as much strength in edge-grain to edge-grain joints as any PVA or water-resistant PVA, but performed as poor as poly in edge- to end-grain joints. Its key property, though, is its long open time; and before the days of Titebond Extend and Titebond II Extend, white glue was the only way to work with complicated assemblies. If you can't find Extend formulations where you buy glue, consider white glue as a substitute.
Made from animal hides, it's favored by musical-instrument makers and furniture restorers because warm water softens the glue, allowing the joint to be disassembled and reassembled without damaging the wood. Crystal hide glue smells foul, and in our tests fell far short of the bonding strength of today's bottled glues.
However, Titebond's Liquid Hide glue, made from the same basic stuff as crystal hide, is cooked at the factory with stabilizers added, and performed on par with PVA glues in the strengthof-bond and heat-resistance tests. Yet joints made with Liquid Hide separated easily in the presence of moisture, just like crystal hide. With the performance, price, and availability of Liquid Hide, we can't make a strong case for using crystal hide in your projects.
Traditional hide glue, above, comes in dry crystals that you mix with water and heat in a pot. Titebond's premixed Liquid Hide glue proved far stronger and easier to use in our tests.
We like two-part epoxy in the WOOD® magazine shop because it bonds wood to almost anything, including nonporous materials, such as glass, steel, and brass. Structural epoxy (labeled with a one-hour or longer working time) is waterproof and approved for submersion, which explains why it's a favorite among boat builders. It also bonds well with oily exotic woods, such as teak. The edgegrain to edge-grain joints we made with epoxy in teak were stronger than the wood itself.
Although the furniture industry has long used this fast-setting glue, it has been available to consumers for only about two years. Like hot-melt craft glue, HiPURformer glue cures quickly as it cools, so you can literally "clamp" a joint for less than a minute with your bare hands. But the bond formed by hot-melt polyurethane is far stronger. In fact, we made end-grain to end-grain joints with HiPURformer and they held up to nearly 1,200 psi of shearing pressure before.
Impressive performance comes with a high price tag, though. The HiPURformer system costs $100, with 50-gram replacement glue cartridges (about 70 linear feet of adhesive) running $7 each.
Titebond's HiPURformer system, below, uses glue cartridges in a heated gun, and the three formulations of glues have different open times (30, 60, and 75 seconds).