Smooth-On Mold Star 30-1A:1B Mix by Volume Platinum Silicone Rubber - Pint Unit

I've been following this company for quite a while and I've used some of their other products such as Body Double and the level of quality in the final molds are breathtaking. What drew me to using Mold Star 30 is not only it's easy mix ratio of 1:1 by volume (you can also mix by weight, which I did for my current project in the pictures), its low viscosity makes cast complex parts and 3d prints easy.When you get these, stir each jar VIGOROUSLY with SEPARATE mixing sticks (I used a silicone stir stick or a drill with a mixing paddle, just drill slowly)! Not using separate sticks will cause cross contamination and you'll ruin the material. I also love the colours which helps with knowing when it's mixed, you don't want streaks in it.Now, prepping your part for molding takes some planning on your part and having sulfur free plastilina clay is HIGHLY RECOMMENDED and IMPORTANT, especially on wood mold boxes. Once the two parts are mixed in a cup you have 45 minutes to pour it into the mold. And I like that because I'm not rushing to pour and 45 minutes is PLENTY of time to stir the material and ensure a proper mix. In that time, you check your dry mold, fix a few things, and even take time degassing the silicone (the vacuum pot is optional).After pouring, you'll have to wait 6 hours until it cures. I ended up sitting the mold outside overnight to cure and doing this on a hot summer night helps immensely, especially when using the cups to check on curing. It was 97°F when I poured the silicone and the leftover material was already fully cured 3 hours later! Wow.The only knock I have on this product is the pricing for a pint and the price kept fluctuating here on Amazon, but you get what you pay for. This stuff is high quality and having a few pints actually is a good thing too, so you'll actually use it.Overall, this is easy to use but the learning curve mainly hinges on how well you plan your design and your mold boxes. Also, doing this outdoors helps with odors depending on what region you're in, especially where the air is drier. Once the price falls back to normal, I'll be getting more of these.ADDENDUM: My masters are done in PLA. For those of you who are using resin printed models, make sure the resin is COMPLETELY UV CURED before using this.

Mixes together quite easily, and produces a flexible rubber that retains its shape when hardened. Both parts store separately quite well for a very long time, even after opening.

Works great and just as advertised as long as you follow the directions. The manufacturer recommends you pour equal amounts of part A and B into separate containers, stir them, then mix together in a separate container and stir, after which they say to pour into a fourth container to finish mixing. I've made a few batches now and as long as you be sure to mix very well (no limp-wristed stirring) then you should be fine without pouring the mixture into a fourth container to finish mixing. Just scrape the sides and bottom of the container well, and the pot life is 45 minutes, so you won't run out of time mixing (not even close).The finished silicone produces a semi-hard but pliable rubber. I'd compare it to the rubber that condensation-catching mats are made from, the kind that line a bartop (can't think of a better name for them), maybe just a little harder than those though. I made a few molds for concrete out of this, and while they weren't the most intricate there were still some angles in the one-part molds that I was worried could wear or break when pulling the concrete out. The silicone has been pliable enough to remove it with some force, while still snapping back to its original shape. I'm sure on a microscopic level, all the pulling will wear it out faster, but I couldn't see anything from looking closely.If you're making a mold of something that has a few turns or twists, or strange angles, I'd recommend a two-part mold.It will also grab detail from whatever you're making the mold from, which is both good, and also something to keep in mind as any imperfections left of the surface of your positive will also be on any reproductions made from the mold.

I am not the kind to write reviews often for items I purchase. I write this review with confidence I have purchased a total of 5 of these trial units over the last 2-3 months. I plan to purchase more within the next couple of days. The 5 times I have purchased this trial unit, it never fails, IF you are patient and know how to use the product as indicated. I was a little nervous the first time I worked with it because I did not want to waste $40. I am into the mold making business so this was in important task. It is NOT difficult work with this product if you follow instructions. What is very important, the most important part of mold making is that the container you are pouring the product into is well glued or contained so the silicone does not leak through any gaps. Also, you may want to secure the object you are making a mold from.My initial and ongoing molds have been a success. I have made custom molds for customers and they have been 100% content and satisfied.

So far so good with what I can see on my mold. I read the reviews and was worried about several things. One being working time. Which there was plenty of time. I only used 26 minutes of the supposedly 45 minutes. Second worry was that my product wouldn't be good when I opened them. I used two kits, mixed all four bottle separately. Then I mixed the part As and Bs together with themselves. I then mixed the As and Bs together with a sturdy paint stick in a one gallon paint mix plastic bucket. I mixed them for three minutes by hand. I then degassed the mixed solution for about 3 minutes and 30 seconds in my vacuum chamber. It poured into my mold wonderfully. I did all this at 68° f. Once the mold was poured i moved the temp to 73° for well over the cure time. Im so please with this product I've decided to do a few more. I hope the results are the same. Shipping and all that other stuff went well too.