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<DIV>These pumps are notorious for cavitation and when they do, they don't
dispense the correct amount.The devices are quite convenient to use
though, for any size job, but I always weigh the epoxy directly into my mix
container, on a platform balance scale, as Keith points out. If you want a
really good plastic with maximal properties, the parts
(A&B) should be weighed. </DIV>
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<DIV>MattK</DIV>
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<DIV>In a message dated 1/18/2005 2:30:36 PM Eastern Standard Time,
adam.g@sasktel.net writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>West
Systems also offers hand pumps for the resin and hardener cans that <BR>pump
out the proper ratios. The downside being that you can only mix <BR>integer
multiples of the "one pump" amount, which is more than needed <BR>for small
jobs.<BR><BR>Keith Black wrote:<BR><BR>> Brian, I look forward to Gray's
answer, but I can share my experience <BR>> with West Systems
epoxy.<BR>> <BR>> West Systems epoxy is not a 1:1 mixture like
many of the hobby <BR>> epoxies. As I understand it the 1:1 epoxies have
extra fillers added <BR>> to the hardeners to provide the 1:1 ratio to
allow for easier to <BR>> mixing. West Systems uses five parts resin to one
part hardener. When <BR>> I first started using the West epoxy I tried
measuring the volume <BR>> either in a small mixing cup or sometimes
counting drops (when using <BR>> very small amounts). This yielded very
unreliable results, sometimes <BR>> it hardened, sometimes I just made
rubber. Then I broke down and <BR>> bought a triple beam balance that
measures to the 10th of a gram so I <BR>> can mix by weight. Using this
method I'm able to mix very small <BR>> quantities and it always hardens
properly.<BR>> <BR>> My "guess" is that the hobby epoxies add
fillers such that the volume <BR>> of the hardener is equal to the volume
of the resin.<BR>> <BR>> BTW, for those using the epoxies from the
hobby shop, I highly <BR>> recommend trying the West Systems epoxy. This
stuff is MUCH cheaper by <BR>> volume and seems to be a much higher quality
epoxy. You purchase one <BR>> resin and different hardeners for different
drying times. Also, they <BR>> have a larger variety of fillers for various
purposes, I personally <BR>> like the Colloidal Silica (406) which will
thicken up the epoxy to <BR>> keep it from running, but unlike micro
balloons it is extremely <BR>> strong. (This is not my own discovery, Lance
Van Nostrand sold me on <BR>> the West Systems epoxy, thanks
Lance!)<BR>> </FONT></BLOCKQUOTE></DIV>
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