Silicone Mold Life

[bwayne64]

Hi Guys,
I had a question for the Casting Guru's on the forum. I know that casting resin parts in the molds eventually wears them out. My question is if the molds will deteriorate just sitting on the shelf. Is there a recommended storage for these, as in temperature and humidity. I'm curious, if I cast a rare part, should I make more than one mold of it. Anybody who knows please post. If you've had molds for a long time, I'd be curious about their condition. Thanks,

Joe C

[427 Cobra]

I myself don't do resin casting at this time, but from what I've heard:

Moulds last three to four years moderately used. If you do this all the time, you have about three to six months storage without silicone spray. You'll want to keep these away from light, and keep them wet with silicone spray, but don't inhale the fumes. This causes a condition known as "silicosis" ,which causes scar tissue to form in the lungs. Whereever these droplets attach themselves will not be able to cough them out, as they are so viscous, and the body doesn't absorb them. In turn, it causes scars to form around them making it so the bodies' oxygen absorbtion is depleted. And over time if there is enough scar tissue, the body can't process enough clean blood. This makes you die of slow suffocation, and it causes necrosis (rot) within the body. Latex paints, and other products with latex in them cause this condition, so always wear protection. I learned this when I was a member of the local painters' union.

It also depends on how soft the mould is, and how often you use it. When the parts start to show a rough appearance, and distort, this is when you want to replace them. Make more than one part, so if you want to use it for casting later, you'll have it. Most moulds last around 50 uses before being worn out. Usually, most people will mark when they used their moulds, and if they don't make 50 parts, they'll sell them to someone else. It's also a good bet to make more than one mould for a backup. Colourants don't usually affect these, but you'll want to be careful - don't take any chances! I'd use a colourant if you're doing production models, and you want to mark your work as Mike Salzo does.

Resin gets hot, and it can distort after a while from repeated use. The shorter the casting time, the hotter the resin. This can lead to early failure - 20 casts less than with a slow curing resin. It all depends on what resin type, and how often you use your moulds. This will limit shelf life. If you're planning on only using the moulds you've made for only a few parts, then the shelf life will be longer. Some people have had these stored for years without damage. You might want to pull these out every six months, then make a cast, and measure it to see if the mould has distorted in any way.

[darkimmitator]

And that resumes today's lesson class !!! LOL ,Excellent tutorial ,Chris ,I am getting ready to start a few castings and this is some good info .Thanks for posting this .

[JAWS]

Im definately no guru but I always keep the first cast seperate if I don't have the master(actual part, production or scratched. When Im finished doing my casting I spray the mould with 'Smoothon Universal Mold Release' I believe its like vasaline. I then wrap the mould in glad wrap(kitchen wrap) & store in a dark place. I don't know if this actually helps but my intuition just sort of tells me it would or should.

[darkimmitator]

UUMMM. Somemore usefull tidbits. Thanks ,Jason.

[427 Cobra]

What you're doing,Jase - is what is supposed to be done. Keep those moulds lubricated. One member of one of these forums said that he does this every three months,and he keeps them away from light - both artificial as well as natural light sources as this degrades the urethane, platinum,and tin based silicone materials. My experience with RTV is that you want to keep this lubed at least once a month for soft silicone, as it has a tendency to shrink until hardened if you don't. Also,don't leave moulds on top of each other - the weight will distort them! If you have a two part mould,spray them with silicone release agent,then wrap them with Saran wrap and lay them side by side in a cool dark place. One part moulds are OK,but don't lay anything on top of them either,just to be safe.

[bwayne64]

Wow, thanks guys. I knew I was in the right place, I'm going to start casting soon, when the weather is right. It's good to know that the molds can sit for a while and still be usable. I have plenty of space to store them. If I borrow a rare kit or part, I can make a mold and have them for a while. Thanks for the great info guys, Cheers,

Joe

[427 Cobra]

(03-12-2010, 12:41 PM)bwayne64 Wrote: Wow, thanks guys. I knew I was in the right place, I'm going to start casting soon, when the weather is right. It's good to know that the molds can sit for a while and still be usable. I have plenty of space to store them. If I borrow a rare kit or part, I can make a mold and have them for a while. Thanks for the great info guys, Cheers,

Joe

Sure thing, Joe. This is what we're all here for. Unlike some snob forums, we are proud to share our reference when we're allowed to,and our knowledge with each other humbly in the spirit of giving in order to further the world of creativity. We're proud of our members' work, and we're also proud to be the latest modeling forum on the internet. Although we're not high tech talkers - our experience makes up for all the CGI computer geeks the world over! We're true artists that aren't stuck up with a high, and mighty attitude towards those of us who aren't as adept as we are,or those who are just begining this hobby. Remember - when your hobby becomes work, and no fun, it's time to leave it. This is why we try to maintain a friendly atmosphere without pressure.

With reasonable care, these moulds will last their lifetime of casting. You just want to ensure that these don't dry-rot. Without being lubricated, they lose their suppleness, and they break down exponentially. They need absorption of the main component - silicone to keep the surface soft, and pliable. This makes for a better,and more reliable casting. This keeps surface defects like warpage, out of the cast parts. The thinner the wall of the mould, the more silicone spray it'll need to be supple. Meaning, it'll need to be taken care of more often than thicker silicone moulds will,but they all need this care periodically, just thinner walls will be less resilient to warpage,or weighted objects laying on top of them.

Keep in mind, all things need maintenance to keep them like new. You can't help the fact that these will wear out eventually,but if you take care of them, they'll last longer than those who don't. You might get 10 more casts than someone who neglects to spray these. The only ones who don't are those who do production types of projects that only last a month, or so. This means that someone who makes more than 50 of a certain part will use these until they're no good anymore,because they're in constant use, so they'll reach the end of their life span sooner than someone who only uses them occasionally.

Most producers make more than one mould if they're going to make more than 50 - 60 parts per run of a single part. One way of getting around the 50 parts problem is some people will make a gang mould where more than one, or two parts are made at once. This saves time,and it makes parts faster, it also saves silicone. For example - a batch of ten parts made from a single mould used 10 times to make a ten part mould can be used 5 times to make 50 parts. Always wait for about 10 - 15 minutes for large parts to cool, or they'll come out warped from the heating of the resin. These will need to cool before being removed as this too, may cause the mould to distort from being handled with hot resin in it. I don't know how many people are going to make moulds for more than that, but this should give you all you need to know about mould durability.

[bwayne64]

Thanks Man,
This is a great forum. Just the business of building, and not a lot of drama, I plan to make a lot of molds for multiple parts. That way I won't waste alot of resin or rubber. The Galactica will probably need a ton of rubber and resin herself. I appreciate the feedback. I will definitely use the info, Cheers,

Joe

[modelnutz]

If you are expecting an exceptionally long run of a casting...make a mold "box".

Place your mold (cavity side up) into a foamcore ( or lego ) box which has 1/4" clearance all round....( I use a few drops of Super Glue to hold the mold down...keeps it from floating )....then, mix up a big batch of resin and pour it into the box completly covering the mold.....about 1/4" over the highest point....place into the pressure pot just like you were casting a part....when the resin is cured take the box out of the mold...take the box apart and remove the mold from your resin "mold box". You now have a "negative" copy of your mold.

This "mold Box" will last nearly forever..allowing you to make a copy of the original mold whenever you need one.

[JAWS]

Oh that is just wicked! Thanks for that tip, that is surely an excellent one to remember.

[Richard_2001]

Interesting a mold of a mold

Slick!!!!!!!!!!!!!

Richard

[modelnutz]

(03-16-2010, 12:25 PM)Richard_2001 Wrote: Interesting a mold of a mold

Slick!!!!!!!!!!!!!

Richard

Tecknically, a casting of a mold
But you get the idea