New tricks with Hide Glue Pots

Although PVA has its place, there are many situations where I prefer to use traditional scotch glue. It is more rigid over time, and can de disassembled in the future with hot water or steam. Unfortunately as an amateur I might want to glue up one set of joints in a month, and therefore I need small quantities, but available quickly and with minimal waste. Messing with jam jars and pans is not safe, so a proper pot is called for. However there are two main drawbacks with traditional glue pots for hobbyists like myself using small and infrequent quantities, apart from the extraordinary price of a cast iron pot. Firstly the glue dries out after use to a hard lump that is very difficult to re-melt, so unused glue is best discarded. Secondly the glue can react badly with metals such as cast iron, forming black hard lumps of degraded material. It makes no sense to cover the water jacket, but leave the glue exposed! The best modern pots seem to have stainless liners, but they are usually electric and very expensive. I made my own water jacket pot from two stainless steel kitchen canisters from a “Pound” shop. The inner has a close fitting lid (with a 1mm vent hole!!) to which I attached a large cabinet knob, and is suspended in the outer canister using two 4mm stainless screws and locknuts. When filled with boiling water the inner heats up very quickly. The open water jacket can be topped-up easily, and also allows the brush to be washed out, as well as being a source of water to thin the glue as it is used. Once cooled and lidded, the glue stays in its “gel” state and seems to have unlimited shelf life, certainly weeks. I have used glue in April that I mixed the previous autumn with no obvious loss of strength and no putrefaction.Addition of a small amount of acetic acid, or white vinegar, to the melt will improve shelf life when cold. It is important that every screw, nut and fitting is stainless steel (including the one holding the knob to the lid!) to prevent any reaction with the glue gel during storage. Brass is not good enough. The inner should be wiped round after use so as not to glue the lid to the pot. Even so the lid usually will only come off when warm. The 1mm vent hole drilled in the lid is big enough to stop the lid blowing off unexpectedly during heating, whilst being too small to allow drying out when cold. The thermostatically controlled heater is a dry iron with a couple of legs added to stand it level. N.B. You will need a knowledge of electrics to know if any particluar iron is safe to use in this way.

About hide glue.

Made from rendered down animal bones and skin, mostly by-product of meat production. Used for hundreds of years. Used to come as hard cakes, like plot toffee. Now usually as gel-state "pearls" which are lentil sized beads with a consistency of Rowntrees fruit gums (sorry for non-UK readers). To prepare, put an amount of pearls, or broken glue cake, in the inner pot and add enough water to almost cover. The first teaspoonful can be white vinegar or acetic acid if you have it, to help it keep in the Jarviser sealed pot. Cakes must be left overnight, pearls can also be left overnight or you can heat straight away. Put the hot water in the outer jacket and bring the WATER to the simmer. I usually do this on the kitchen hob, then transfer to the workshop iron just to keep below boiling. The glue must not boil. Stir until all the lumps have melted. The consistency when ready should be like single pouring cream. To thin it you can add a little hot water using the brush dipped in the water jacket. This is a feature of my pot, but cannot be done in traditional pots. In cold weather, you can warm the joints with a hot air paint stripper gun first.