comparing rubber mold kits

[sabanknight]

Hey, looking at a pair of mold making compounds. I have used alumilite in the past so it was my first choice but decided to shop around. the two I am looking at are
Mold Max® Series Silicone Product Information | Smooth-On (specificly the moldmax 20 or 25)
and
Alumilite - Products - Silicone Rubber High strength 2

The 1 gallon mold max seems to have close stats, I am mainly concerned with the tear strength since the lower alumilite at 45ppi tore and crumbled under my abuse after using it some 10-12 times. also with the tear strength both seem to use a different measure 0o alum uses ppi and max uses pLi, typo or are these both measurements and what is the conversion?

The other thing that caught my eye was the big one $$$ max's 25 sells for $94 per gallon(11lbs) and alumilite sells the highstrengh(that seems to have similar stats) at $165 for 10lbs! Is this just crazy markup or is quality a factor?

anyone see any gaps in the stats or have used mold max and can atest to its quality? or in comparison to alumilite products?

 

[darthweezy]

sabanknight-

The product from Smooth-on is top notch! I've used a few different kinds of silicone from them and I love them all. The Oomo products are great for quick molds but the molds don't have a high shore strength and subsequently don't last long. They work well for one-sided casts such as custom bases for Warhammer 40,000 miniatures.
The shore 20 and higher silicones are great for general molding; I tend to use these the most.
I've also used the paint-on silicones for weird-shaped sculptures or really high detailed models as you can paint layer upon layer to catch fine detail. I've used this when I scratch-build Tyranid terrain for Warhammer 40K.
I've never used them for any type of pressure-casting or other types of casting as I am not that advanced yet, but I'm sure the pros will respond soon!
By the way, the resin from Smooth-on is also fantastic!
Hope this helps!

 

[Bondo Fett]

What Darthweezy said. The Oomoo product captures detail excellently and releases resins easily, but it is not very durable- you can pick chunks of it off with your fingers. Smooth-On's Rebound 25 is a brushable type silicone and it is very tough. Great for complex shapes. I'd like to hear form the Alumilite crowd.

 

[sabanknight]

What Darthweezy said. The Oomoo product captures detail excellently and releases resins easily, but it is not very durable- you can pick chunks of it off with your fingers. Smooth-On's Rebound 25 is a brushable type silicone and it is very tough. Great for complex shapes. I'd like to hear form the Alumilite crowd.

so... the Mold Max® 25 Shore 25A tin-cure silicone rubber is the one you can pick pieces off with your fingers easily? the high strength alumilite takes some work to get some work to get off the main body of the mold unless its a real thin piece. As well it has some decent undercuts and I can bend the mold end to end with no sign of weakness. I would be curious to know what stat represents the durability as I thought the tear strength represented that. Or are you not talking about the Mold Max® 25 Shore 25A tin-cure silicone rubber?

 

[Bondo Fett]

I was commenting on on the Oomoo line from Smooth-On, I've never used their MoldMax product. It wasn't meant as a slam either to say you could pick pieces of the silicone off, only to say you can tear it if you try. It is a great material for simple, one-piece box molds that aren't expected to hold up to "production" levels of cycles (more than ten, I'd say). It easy to use, as well, simple one-to-one volume or weight. Its a pourable rubber, shore 30 hardness (the higher the shore #, the harder and less flexible the rubber). If you have significant undercuts on your model it might tear the Oomoo when de-molding. Can you post a pic of your project? It might help with recommendations since there are so many different types of rubber designed for different applications.

 

[coldin71201]

Smooth-On 25 all the way. The pink stuff. I use nothing else.