Cure time on RTV silicone?

[outdoorzman]

Okay, so I'm new to using RTV silicone and am curious if my molding is salvageable.  I'm using Silicone Inc's GI-1100 to make some glove molds of fins.  I measured out the silicone and activator (shaken of course) using a digital scale, 10 parts silicone to 1 part activator.  For one of the fins I used 4 oz of the silicone and 0.4 oz of the activator.  I spoke with a friend and think now that maybe I should go with grams.  Also, my scale only goes to the 10th of an ounce.  Anyway, I poured the thoroughly mixed silicone (no streaks, all uniform blue) and it has been 24 hours... the silicone has firmed up, but has not fully cured. I screwed up perhaps on the measure of activator (obviously not enough).  I did use the same product in a class; the color of the uncured silicone is the same as the glove molds from the class, but I recognize that the dye lot may be different and so that probably means nothing.  My question is: will they potential cure fully in 48 hours or should I just scrap them and start with some fins off a similarly sized fish?  I'm not sure what to do.  I did mix up some more silicone tonight, using gram measurements instead; I'll find out in the morning if those cure properly.  I'm very disappointed as I thought I had everything right  .  Any advice or input will be greatly appreciated.

[Mike B.]

This time of year the cure for the GI-1100 will be slower because of the cool dry wheather. If you make a little heat box (card board box will do) add a light and a cup of water it should cure the silicone for you. GI silicone is a tin based rtv and heat and humidity will make it cure faster. Measuring in grams is a lot better go buy digital food scale you can get them for around $20. This time of yeare if you want a faster cure with the GI RTV you may want to get some UFC to help speed the process.

Mike

[outdoorzman]

Thanks Mike, I'll give it a try with the light and cup of water.  The shop is at about 73 degrees though it is very dry!  I'll add some humidity to the equation.  I am using a digital food scale; however, it only goes to the tenth of the gram (is that enough accuracy?)  I did mix some more up last night using grams and it worked out just fine... so, I'm pretty sure my activator amount was a tad low.  I'll try boosting that humidity and see what happens.  Thanks again.

[Mike B.]

Measuring to the gram is fine. By ounces or tenth's of ounces can give you trouble though.

[outdoorzman]

Well, the box seemed to work quite well.  Thanks again; I do believe I can salvage these molds.  I'm using gram measurements, but it still seems slow to kick.  Perhaps the shelf life on this bucket of RTV is past...

[Polymer Guy]

Thanks Mike Bush!  You are the man!  Yep, tin based silicones need that moisture, (condensation cured) so the creation of humidity works great.  Also, if you received your silicone in the summer and are pouring in the winter, you may have a longer dwell time, as silicone manufacturers will sometimes change catalyst levels to help control the speed of the system in the summer and winter.  So if you have a "slowed down summer version" it will take longer to cure in the winter unless you use the good ole "humidity in the box" method!  And yep, this method works great. 

[outdoorzman]

Well, I've pulled about a dozen fins and they look great!  The molds are perfect; it just took about twice as long... the humidity in the box did the trick though!  Thanks Mike.