Back in the shop, spring is just around the corner.
March 16, 2023
Glues a sticky subject
I use a variety of glues in making my landing nets, and I would like to pass on my thoughts and understanding of this subject to you.
First I would like to talk about glues in general. I like to separate glues by their primary property.
A. Reactive or catalyzed glues. This group includes the epoxy resins and resorcinol glues (These glues typically are a two part glue with a resin and harder.) The glue may react with the natural lipophilic resins, phenols (natural alcohols) or saccharides (complex sugars) in the material glued to form their bond. In some cases such as the epoxies, they may rely mainly mechanical adhesion with the microscopic surface imperfections.
This glue does require mixing with water before use and can not be stored in a mixed state. It has a couple of disadvantages. Historically it was formulated with excess formaldehyde. This caused it to give off the excess formaldehyde when it was mixed and used. In the current formulation this is much better controlled. The current product meets national and California standards for release of formaldehyde. Good news, well sort of. It means that the chemistry of the product has changed. There is a recommended minimum pot time of 15 minutes. ?What? This means you should let the glue sit for 15 minutes before you use it, to allow for the glue to start catalyzing. The glue has a working time of 30 minutes ( time from application to final clamping) and a pot time of about 2 hours.
I have had students who report problems with adhesion. I have not had problems with this but I have some insight. The product you receive is really a two part product. The resin and catalyst are mixed in the same container, along with a wood dust filler. Typically this is sold in a plastic container. Plastic containers ARE NOT moisture proof. Most manufactures suggest a 1 year shelf life, when stored until normal conditions. Most of the glue I have bought over the years has been okay. When Dapp stopped making this product there was some post date product being sold on the internet. I am now buying this glue as Pro-glue. (Check Joe-woodworker.com or Vac-u-clamp.com ) (Woodcraft carries this glue but in 5 gallon buckets, go figure.) Cascamite is another brand available on Amazon. It comes in a 220 gram tub. Given that it takes about 3.5 oz or 100 grams to glue a net, it is a pricey product.
I have not had adhesion problems, EXCEPT once early in my experience. I glued up a very a beautiful curly maple net. The glue seemed a little crumbly in the plastic container, but I broke up the chunks and mixture it with water. So good so far. Glue up seemed okay and it dried into a nice powder as the net fell completely apart. (A similar event happened to a friend who let the net freeze in his shop before the glue had dried.) I now store the glue in GLASS jars to avoid atmospheric moisture activating the glue. AND would NOT use the powdered glue if it has any caking (dry lumps of glue powder).
This type of glue is still used extensively in the veneer plywood industry, where they use radio frequency to set this glue. (micro wave) As I have read the industrial literature about this glue one important point, that has not been pointed out in the general information, is that this glue is best “dried” / “set” in a 110-140 degree environment. One of my students tried this glue and let it set in his 50 degree shop. The whole event was a mess. I use a “hot box” (a shop made box with old fashion light bulbs for heat) to cure the glue. I have also used a small electric space heater in a bathroom for larger projects.
Two last insights about this glue. When you mix it, put the powder in a bowl (I use one hemisphere of cheap rubber ball and a silicon spatula) Put in a SMALL amount of water, mix that into a paste then keep mixing and adding water until you have the right consistency for the batch. Let it set for 15 minutes, (you may need to add more water before using).
I wear rubber gloves when gluing up a net, to protect my hands. When I need to clean up the glue from my hands, I use a mixture of white vinegar (1/3) and Joy dish washing detergent (2/3). (This glue is made by adding acid to urea, the acid in the vinegar and the ammonia in the detergent upset the chemistry of the glue and make clean up much easier.) (Dawn detergent doesn’t seem to work).