OOMOO 25 VS OOMOO 30

I have discussed this once before, but I think it needs refreshing.

I use Smooth On products.  Its all I have ever tried.  Having a distributor 10 minutes away makes it that much more attractive.

The Smooth On Starter Kit comes with OOMOO 30.  This is a medium setting Silicone.  It has a 7-9 minute pot life and cures in roughly 6 hours.  This is what I use the most.

OOMOO 25 is a much faster setting Silicone.  It has a pot life of 2-3 minutes and cures in roughly 2-3 hours.  It says 90 minutes, but its still tacky after 90 so I leave it a few more hours.  The benefit of using the OOMOO 25 is that it is a quick setting silicone.  I use it for what I call Stage Molds.  Stage molds are basically one time use molds.  You make the piece in stages.  You make a mold of a built up area then carve/sculpt it.  Then you make another mold of the sculpted piece and either use that or rework the piece some more.  Its like saving your work in case you slip with a knife or cut too much off in one area.  Thats why I use it.

Its also good if you are making only 1 or 2 small molds.  Remember you have to mix it and pour in under 3 minutes.  Proper pouring procedure of silicone is a nice, SLOW steady stream to help break up air bubbles introduced while mixing.  Plus you need to get it into the pressure pot.   If you are mixing alot of product or have several molds to pour, I dont recommend using the OOMOO 25.

I prefer the OOMOO 30 except for the 6 hours cure time.  But thats the time it seems to take for a good solid mold so I live with it.  I like the detail the OOMOO 30 provides over the OOMOO 25.  Because it has a longer pot life it doesnt thicken up as quick.  So I can pour several molds properly without fear of the silicone curing before I can get it into the pressure pot.  Also, because it stays in liquid form longer, it can get into all the little tighter areas nicer and cleaner.

Resin Mixing Ratios

Every resin has a mixing ratio.  The ratio is how much of Part A to mix with how much of part B.

And then there is the fine print.  The wuh?  Yes...the Fine Print.  Fine Print is what we dont see because we think we know it all.  And then all of a sudden everything goes kerfluey and we dont know why.  Because we didnt see and read the Fine Print.

The Fine Print says...Mixing Ratio "X amount" of A: "X amount" of B......and this is the important part...By Volume "X amount A: "X amount" B by  Weight. 

And some resins, MOST in fact have 2 ratios.  1 ratio is for WEIGHT and 1 ratio is for VOLUME.  The weight ratio is the one that is usually the weird ratio.  100:80 or 100:90.  The volume ratio is usually closer to a 50/50 or 1:1 ratio.  Last week or so when I first made the Roboid molds I was having issues with my urethane resin.  Why?  because I was confusing the volume and weight ratios.  I was trying to measure the weight and instead adjusted the volume and it impacted the resin in a negative way. 

You cant measure weight with measuring spoons.  Measuring spoons measure volume.  And thats exactly what I did...or attempted to do. 

Since I dont have a scale, I have been measuring by volume.  When you get the volume ratio right, the weight ratio will be correct and visa versa.