mold rubber type 3 doesn't harden!

...I realize that this is an old post, but I have incurred in the last couple of days the exact same issue...recent purchase of HS 3 from a well known big box store (3-5-16) used a digital scale (Grams) to measure out a perfect ratio and here it is now aprox. 72 - 80 hours since the pour. The rubber is tacky and very soft/ pliable...I hesitate to remove any of the clay that forms the box in fear of tearing the already poured rubber. The pour consist of 50 grams of rubber with the correct amount of catalyst...first part of a 2 part mold.

I figured 1 Gram of catalyst for every 10 Grams of rubber...worked perfect with a larger gang mold I did using HS 2...newer product perhaps? vs. older HS 3 product (store shelf life)....I buy one day and either pour that same day or the next.

Mixed the rubber and catalyst for aprox. 30 seconds...it appeared that the catalyst was mixed in well with the rubber...should I have continued mixing ....say another 30 seconds or so.

Relative Humidity @ 50-60 % room temp @ 70 degrees f. No other sources of heat or moisture in relationship to the mold setting up.

Any suggestions??

.....I should have read a little bit deeper in the technical data sheet....my bad... I did not realize, till now, that that HS 3's hardness is aprox. half of HS 2's which could present an issue with multi part molds and the use of rubber bands to control the amount of pressure being applied to the mold....too much give in the mold will cause the poured resin piece to be distorted. I will, more than likely, use up what's left of the HS 3 on some single part molds and go back to using HS 2 on the multi part molds....the only reason that I switched to HS 3 was it is available (when they have it in stock) at the local Hobby Lobby for aprox. $19.00 using the 40% off coupon ....going to give the locally owned hobby shop that I patronize a try and see what HS 2 will cost me and how long it will take to get it....I get a 10% military discount there and he always treats me right.

The tackiness is less this evening.....should be all but gone within the next 24 hours....will pour the 2nd part of the 2 part mold using the HS 3 this weekend some time....I can control the room temperature and humidity levels where I pour so I will increase the humidity to the high 60's lower 70's percent range and see if that will speed things up some.

I have started using Price-Driscoll Ultra II paintable mold release in a spray can...I spray the piece that I am molding and the inside of the mold box with a mist coat....perfect release when using Alumilite HS 2 I haven't released anything from the HS 3 mold yet , but I am sure I will have the same results    I will use a lite coat between the two (or more) halves along with a coating of Vaseline for insurance. 

Holding two part molds without distortion can be done by casting a plaster mold jacket around the masters. They can then be banded together without deformation. Very soft molds can benefit from the addition of alignment furniture embedded or cast into the plaster halves. Definitely cheaper than throwing out an otherwise perfect mold in HS3!

Best regards!