300 Mini Pumps. To buy or not to buy?

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Selling WEST SYSTEM Epoxy in a retail environment for more than 20 years, the most common question I receive is:
Do I really need the Mini Pumps?

We’ve all been in a situation where the salesperson is trying to up sell us or has no clue what we really need. In the case of Mini Pumps, however, the salesperson is trying to do you a favor. You really do need Mini Pumps unless you already have a set of them, or you plan on using a scale.

Why Use Pumps?
WEST SYSTEM Resin and Hardener—like any epoxy—must be mixed at the correct ratio to cure properly and with the published physical properties. Too much or too little hardener will not change the speed in which it cures but instead will prevent it from properly curing. Too much hardener means once all the resin has reacted with the hardener, the extra hardener has nowhere to go. This extra hardener in the mix results in softer epoxy, or what the industry calls a “plasticizing cure.”

We formulate the ratio for 105 Resin and our 200-series hardeners to have a “fudge factor” but get outside of that forgiving stoichiometric range and problems will occur.

Mixing on ratio is always ideal, but with WEST SYSTEM products, hardener lean is better than hardener rich. This is why you really want to buy a set of calibrated 300 Mini Pumps. One full pump stroke of resin to one full pump stroke of hardener will yield the proper volume of each.

WEST SYSTEM is based on the 105 Resin and four 200 series hardeners (205 Fast, 206 Slow, 207 Special Clear Coating, and 209 Extra Slow). WEST SYSTEM pumps are supplied in the following pack sizes which have been calibrated to the 5:1 mix ratio for 105 Resin with 205 Fast and 206 Slow hardeners, and 3:1 mix ratio for the 105 Resin with 207 Special Coating and 206 Super Slow hardeners:

Getting the most out of Mini Pumps
Now that you made the right decision and bought the pumps, here’s how to make the most of your purchase.

When you first install the pumps, check to make sure the resin pump is ready to use. Hold the white cap that screws onto the can and the clear plastic pump barrel and make sure they are screwed together snugly. You will also want to check on this from time to time.
Priming the pumps before the first use is simple but important; the instructions in the package explain how to do this. You will want to check the prime if the pumps been sitting for a long time, or when changing containers.

That’s right, when changing containers. No need to buy new pumps every time you buy a new pack. Store the pumps on the container and when you run out of WEST SYSTEM Epoxy you can move your pumps to the new resin and hardener.

If the pumps have been sitting for a while they may develop a crust on the end of the spout.Hardener pumps particularly seem to do this. The crust is easily cleaned away: just break it off and wipe the spout. You can use warm water to clean the hardener pumps and acetone or denatured alcohol for the resin pump, if needed.

Use only full pump strokes and do not pull up on them, let them return on their own. Alternating one stroke of resin and one stroke of hardener eliminates the need to count strokes and reduces the time spent waiting for the pumps to return to the top of their stroke. Slow pump return can be an issue when using epoxy in cooler weather when the epoxy becomes “thicker” (actually, more viscous as our chemists would say). Try to keep your resin and hardener warm even if what you’re working on isn’t. Mix your epoxy indoors if you’re working at low temperatures in the garage. In the boatyard, an empty cooler and a shop light with an incandescent 15-watt bulb will keep your resin and hardener nice and warm.

Remember, warm epoxy will cure faster until it hits the cool/cold surface. Call and talk to one of our Technical Advisors about cold temperature bonding applications, or check our User Manual & Product Guide, visit westsystem.com.au, or see “Cold Weather Bonding” by Don Gutzmer in Epoxyworks 43.

Extract from the Gougeon Brothers publication EPOXYWORKS Issue Number 47:Fall 2018. Reprinted with the permission of WEST SYSTEM Inc, USA.

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