Official Luthiers Forum!

I just got a bunch of West System epoxy in and I ordered the little pumps for them.

For those who use this stuff do you just leave the pumps in place for ever or remove them and seal the can back up after use?

I tried the pumps once and didn't like them. They require you to mix a fairly large quantity of epoxy which was far more than I needed unless I was laminating a large panel. Also, they started to get inaccurate and lose their prime after a few months. I switched to a small electronic scale and have never looked back.

For epoxies that do poorly if they are not mixed in the proper proportions, I’m like Barry. I find volume to be a frustrating method of mixing. Weight is much easier to get just right.

Weight here too...

The pumps are handy for boat building, not so much for laminating guitar parts. As Barry mentioned their accuracy fades over time unless you keep them maintained. For the small quantities of epoxy needed to laminate back and side sets I use an old triple beam balance and zero out the container I'm adding the epoxy into. I first measure the hardener into the cup and then add the resin. that makes it easier to compensate for any mismeasurement of the hardener. For very small quantities I have filled dropper bottles with hardener and resin and then count the drops to get the right mix.
Epoxy goes a surprisingly long way, so if I am not sure how much I will need I will err on the side of too much, but try to have another little side project to use the extra on.

For boat building and other high use activities, I think most people do just leave the pumps in place and then clean them up when changing cans. I initially used them but with my slow rate of use they "failed" before the first gallon of resin was used up.
Some boatbuilders who use larger quantities will also forgo pumps and instead mark two containers with "fill lines" and then dump into a third container to mix in.
One suggestion I would make is to buy a box of disposable nitrile gloves and always wear them when working with epoxy. That stuff has a way of getting on your hands and cleaning it off with alcohol as I have done is not a good idea. I also like to cover my bench with paper when working with the stuff and wear old glue stained clothes that I don't mind getting ruined.
But it is good stuff!

I would definitely still weigh the portions but what I am wondering is if it's bad to leave the pumps in there. It won't harden I guess unless it gets contaminated but would air getting in there be bad and or does it leak epoxy fumes into your workshop?

When I used the pumps I never noticed any problems with fumes or strong smells coming from the cans. The pumps generally retain some epoxy in them so the epoxy/air surface contact area is relatively small. When not being used a lot the pumps can lose prime and can "burp" giving less than a full "pump" and throwing off the mix ratio, but if you are weighing the materials before mixing that should not be a problem, as it can be for those who mix using the alternating pump method. Sometimes the epoxy will thicken around the spout but can be cleaned off with a paper towel wetted with alcohol.

We had pumps on the MAAS, West, and System3 epoxies in the shop, but mixed by weight for anything less than a full pump's worth of material. Keep a pocket calculator handy to do the arithmetic.

I keep my epoxy bottles in a plastic bag when not in use.

Put a piece of masking tape on the open nozzle of the pumps to keep oxidation to a minimum.

Ah great ideas thanks.

I leave the pumps in place....they will get 'sticky' and fail after a year or so.......I use it mostly for surfboards....1 pump is a lot for a guitar....a scale is probably more useful for guitars...maybe 1/2 squirt......

I've used West Systems' pumps for largish laminating tasks on an aircraft construction project.
For guitars, I found pumps are elephantine things to me. I've happily used disposable pill cups; the epoxy I used was mixed 50/50 by volume and that was easy with the 1-ounce pill cups (think Nyquil cups).

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Peter Havriluk

The graduated 1 oz. medicine cups Peter mentioned are a good way to mix small quantities of epoxy:
https://www.amazon.com/Non-Sterile-Grad ... BFXI&psc=1
For slightly larger quantities I use leftover plastic yogurt and single serve fruit cups my wife buys for her lunch.

Another good option for quantities up to 4 oz. is the graduated specimen cups. Unused, of course. (See: https://www.amazon.com/Vakly-Specimen-C ... 220&sr=8-4)

Never been able to see past syringes for epoxy ratios with the small quantities we use.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

We used an inexpensive gram scale for mixing in 1 ounce poly dose cups and pump or the 10 lb capacity 0.5 gram tolerance digital scale for larger batches.

Dose cups also work well with CA and for small batch color mixing for touch-up work using 1.5mL disposable pipettes to transfer CA to the work and to meter dye or universal tint into finish material, so we usually bought them in 5000 unit packs.

The scale:

https://www.amazon.com/gp/product/B00ME8VI34/

Dose cups:

https://www.amazon.com/Small-Plastic-Di ... B07D3GX2HS

Disposable LDPE micro-pipettes:

https://www.amazon.com/Globe-Scientific ... B00G6T6THM

A pocket calculator is handy for the smaller batches we used for Silvertip pore filler...after using the resin pump to add about 2/3's of what was needed for the batch to a dose cup (already pre-zeroed on the scale), the resin is weighed and that weight multiplied by the sum of the resin and hardener ratio numbers divided by the resin number (e.g., 100:44 by weight for System 3 Silver Tip >>> (100 + 44)/100 = 1.44). Add hardener straight from the pump until the weight equals the target value.

Example: 6.5 grams hardener x 1.44 = 9.66 grams of resin plus hardener

For some of the canoe work we did, and for a portable shooting bench project (the epoxy sealed the two plies and applied edges of the cored Baltic Birch top and seat), we used the pumps directly and 6 and 10 ounce disposable wax-free paper hot/cold drink cups...these cups are sold in 6, 8, 10, 12, and 16 ounce sizes, and will hold up when epoxy is thinned with DA or acetone.

https://www.amazon.com/dp/B01A5WTG9S/

Hope that may help source some useful supplies for the job.