epoxy joint

[Rcmaster199 at aol.com]

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. 
 
MattK
 
In a message dated 1/18/2005 2:30:36 PM Eastern Standard Time,  
adam.g at sasktel.net writes:

West  Systems also offers hand pumps for the resin and hardener cans that 
pump  out the proper ratios. The downside being that you can only mix 
integer  multiples of the "one pump" amount, which is more than needed 
for small  jobs.

Keith Black wrote:

> Brian, I look forward to Gray's  answer, but I can share my experience 
> with West Systems  epoxy.
>  
> West Systems epoxy is not a 1:1 mixture like  many of the hobby 
> epoxies. As I understand it the 1:1 epoxies have  extra fillers added 
> to the hardeners to provide the 1:1 ratio to  allow for easier to 
> mixing. West Systems uses five parts resin to one  part hardener. When 
> I first started using the West epoxy I tried  measuring the volume 
> either in a small mixing cup or sometimes  counting drops (when using 
> very small amounts). This yielded very  unreliable results, sometimes 
> it hardened, sometimes I just made  rubber. Then I broke down and 
> bought a triple beam balance that  measures to the 10th of a gram so I 
> can mix by weight. Using this  method I'm able to mix very small 
> quantities and it always hardens  properly.
>  
> My "guess" is that the hobby epoxies add  fillers such that the volume 
> of the hardener is equal to the volume  of the resin.
>  
> BTW, for those using the epoxies from the  hobby shop, I highly 
> recommend trying the West Systems epoxy. This  stuff is MUCH cheaper by 
> volume and seems to be a much higher quality  epoxy. You purchase one 
> resin and different hardeners for different  drying times. Also, they 
> have a larger variety of fillers for various  purposes, I personally 
> like the Colloidal Silica (406) which will  thicken up the epoxy to 
> keep it from running, but unlike micro  balloons it is extremely 
> strong. (This is not my own discovery, Lance  Van Nostrand sold me on 
> the West Systems epoxy, thanks  Lance!)
>  


 
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