Signs of mold deterioration?

[tubachris85x]

Hey all

I wanted to ask the more experienced molders about this. This is really my first experience with a silicone mold ever, and I have no idea what kind of signs to look for to know when the mold is going south.

I've heared others speak of deterioration, yielding bad casts. What are some of these physical signs, aside from obvious tears, etc.? Sorry if this sounds like a stupid question, but I can't quite understand completly as to what actually happens. Thanks!

-TC

 

[Tim Allen]

One of my 300 helmet molds just died, prior to the "tears" appearing in the mold I would get soft spots in my pulls. Meaning that the dome of the helmet wouldnt have a smooth surface but minor ripples in it. You couldnt really see them in the casting itself but rather feel them in the mold as you ran your fingers across it. Eventually those "soft" spots turned into tears and the mold was retired.

 

[micdavis]

Discoloration of the rubber.

Deformation. Mold does not spring back as nicely.

 

[exoray]

Discoloration of the rubber.

I would say for me the above is the biggest sign, generally followed by the mold actually drying out (fine details start to crumble) losing it's elasticity and the lose of self release properties making pulls harder to get out...

 

[micdavis]

You can extend the life of RTV by using baby powder in the mold and if possible spray a coat of primer in the mold before pouring any resin.

 

[GuntahKela]

To add to the description of mold discoloration, a new RTV mold begins as a blue pastel. As it ages, it becomes a dirty yello-ish color.

 

[Rhett J Martin]

You can always "recharge" the mold for a short time by tossing it in the oven for a few minutes-hours, even an older one. I've used this method often, but be sure to have some solid ventilation. It can stink(and hurt you)!! I'm also NOT positive that this will work for EVERY type of silicone. I've used it with most of Smooth On's stuff, like Oomoo and Mold Max

 

[spcglider@aol.com]

You can always "recharge" the mold for a short time by tossing it in the oven for a few minutes-hours, even an older one. I've used this method often, but be sure to have some solid ventilation. It can stink(and hurt you)!! I'm also NOT positive that this will work for EVERY type of silicone. I've used it with most of Smooth On's stuff, like Oomoo and Mold Max

I believe what that does is force some of the oils naturally in the silicone back out to the surface.

The general rule of thumb for silicone molds is not to count on more than 30 pulls (when using urethane as a casting medium). I've had molds that have lasted well beyond 50 pulls, but they were the subject of EXTREME care in the de-molding.

When the mold starts showing wear, it'll start to have a lighter color (blue silicone will turn almost white) and then it'll get "crispy" and small bits of silicone will start chipping out as they stick to subsequent pulls. Even if you're careful, the little tiny details will turn yellowish and get really fragile.

I guess the most important thing is to remember: a silicone mold is not forever.

-Gordon

 

[Jumpin Jax]

Can one oil the mold to preserve it?