Help with sticky silicone mold?

[CGClone]

Using Smooth-ON Ecoflex 50, I made a mold, typical flat box type. The master released fine, most of the mold is just fine, but I have a few tacky areas that seem to just not fully cured. I've used isopropyl alcohol to wipe it out, etc, do I have any options here to clean this up?

I want to pour urethane into the mold for a flexible armor piece, so Im not sure just what would inhibit what here with those tacky areas. Any input to save my rear would be great. Thanks! (not sure if it shows up in the photo)

 

[JPH]

How old is the mold?

If tacky, Id give it a day or two extra to cure in a cool, air conditioned place.

If it is a few days old...and still misbehavin, you may want to redo. You will spend more time trying to fix it than it would take to redo it.

Also, consider making that part of your mold out of stinky protoputty if supplies and cost an issue

 

[CGClone]

How old is the mold?

If tacky, Id give it a day or two extra to cure in a cool, air conditioned place.

If it is a few days old...and still misbehavin, you may want to redo. You will spend more time trying to fix it than it would take to redo it.

Also, consider making that part of your mold out of stinky protoputty if supplies and cost an issue

Just demolded. So this is fresh. Thanks for your help. I do appreciate it!

 

[Cbstudios]

What was your master made out of? Certain materials can inhibit the cure of silicones, causing sticky areas. It could also be an issue of the silicone not being mixed properly, or even if the silicone is an old batch and has started to go bad.

 

[PropReplicator2]

Could have been a paint if you had any paint sprayed onto your master. I've had issues with that before. No way to cure it. Just give it a few days and if it's still not cured then toss and redo it. It sucks but that's just the name of the game

 

[JPH]

I have used eco flex for molds, and to this day, everytime I use it, the Ecoflex appears to stick to the cast. It makes great cast, but as I slowly peel each cast out of the Ecoflex, I worry that those little adhesive stalks of ecoflex are going to tear, and they have not...YET.

I hope your Ecoflex decided to behave.

I also paint stuff all the time before I use it for a mold, it helps me see defects in it. I usually coat the inside of the mold with lotsa mold release and then run a practice cast through it to pull any gunk out.

 

[Zinger]

You'll probably have to remake the mold. Cure inhibition is forever.
Before you do, test the Ecoflex on the positive again. Clean the positive well with IPA or acetone. Let dry thoroughly. Then paint some Ecoflex on the spots that had inhibition. You might have just contaminated the positive with something while you were handling it. If the Ecoflex cures this time, you should be able to make a new mold.

If the Ecoflex still won't cure, try applying mold release to the positive and test the rubber again. If that doesn't work, try a spray on clear coat. Those may solve your problem, but no guarantee.

 

[CGClone]

To wrap this up and thank you for all your input - I let the mold sit for 3 days after removing the master and everything dried up! Thanks gang. I appreciate everyone’s input.