The pumps are handy for getting the stuff out of the cans, but I actually use small kitchen-style measuring spoons to mix the West Systems. For most Luthier work, we're using small quantities of epoxy at a time. So, I got a set of plastic measuring spoons and found two that are a 5:1 ratio to each other (I think they are 5ml and 1ml). I pump or pour the epoxy into the spoons, and dump them into a plastic disposable water cup (those little ones that are at the grocery store). One spoonful each of resin and hardener gives you 6ml of epoxy. That's about the minimum amount of West Systems that you should mix at a time. I've found that if you try to measure and mix less than that, you'll have problems with it not hardening.
The 105 resin lasts approximately forever, even after opening. I buy it by the gallon, which is cheaper, about once a year. I keep the pump right in the can, and pump it out into the spoon.
However, the 205 and 206 hardeners start going bad as soon as you pop the metal seal on the can. They absorb moisture from the air. The little pint cans are typically good for only a few months, when left open to the air. The little pumps have an air bleed hole, so if you leave the pump in the can, the hardener will go bad quickly. I only buy the hardeners in the little cans, and as soon as I open them, I pour the entire contents into plastic squeeze bottles with air-tight caps. That gives the hardener a life of six months or so. When mixing, I squeeze it right out of the bottle into the 1ml spoon.
Note: The hardeners are nearly clear when new. As they start to absorb moisture and go bad, they turn darker and darker amber color. The darker it gets, the more risk there is that the epoxy won't kick and harden.
Both the 205 and the 206 hardeners are useful for our work. A mix using the 205 Fast hardener has a working life in the mixing cup of about 5 minutes. After that, it will quickly get thick and hot. If you leave a cup of 205 mix on the bench, it will actually start smoking and melt down the cup into a blob. The more volume of 205 mix is together in one place, the hotter it will get! You should never attempt to use 205 mix for any epoxy castings, such as encasing pickups. The 205 mix is great for smaller repairs and jobs where you can spread it on and clamp it up within 5 minutes. The 205 mix will fully harden in 2-3 hours.
The 206 Slow hardener mix is much more forgiving, and slower to harden (8-12 hours). This is what you should use for larger size laminations, such as your body top. It also won't heat up in the cup, so it works for casting. I do my pickups in 105/206 mix with black pigment coloring.
For large-area glue-ups such as a body top, I apply the epoxy with a disposable wool dauber, available from Tandy Leather and other sources. That seems to be the best way to get an even coat on the surface without too much excess thickness. That reduces the squeezeout and mess. I normally apply the 105/206 mix to both surfaces, let it sink in for a few minutes, then put them together and clamp.
Once you get used to using West Systems, you'll probably start using it more and more. I now use it for almost all the glue joints on my basses. In the few places where I don't want to use epoxy, for various reasons, I use LMI's Instrument Makers Glue.
Last edited by Bruce Johnson : 11-17-2012 at 02:56 PM.