Resin & RTV: MicroMark, SmoothOn, Polytek or Alumilite?

bobbyfett · Post by **bobbyfett** » Tue Sep 13, 2005 10:04 am

Hey everyone, I just finished going through every RTV and Resin thread on this board because I'm thinking of casting some parts I am scratchbuilding to avoid having to do it multiple times. It seems as if there are four major brands/lines out there. MicroMark, SmoothOn, Polytek, and Alumilite. I am not sure which one is best for my purposes. I just need something a beginner can use. Something that is forgiving and creates the least airbubbles in both the RTV and Resin. From what I gather, polyurethane resin is best. It doesn't need to set up super fast, but I don't really want it to take a day to cure either. I want something that is least deadly as possible as well. So what are the pros and cons of each? Sorry to start yet another resin thread, but I just couldn't find an answer in the others. We should have a sticky on Resin & RTV like the surface fillers. Thanks for any advice!

chasd25 · Post by **chasd25** » Tue Sep 13, 2005 10:20 am

Go to the smooth on website, and order one of the super sampler kits. Regardless of what you think of smooth on (I love their products, some people hate them), the super samplers are great for the first time user, for very little money.

You get enough material to make a few small molds and castings, enough to familarize yourself with the materials, and how they work, without dropping $100 on materials.

Get the Silicone Sampler:

http://www.smoothon.com/Getting%20Started.asp

You can't go wrong got $25

Charlie

bobbyfett · Post by **bobbyfett** » Tue Sep 13, 2005 1:09 pm

Thanks Charlie.

I had forgotten about that offer. Do you know how much material it actually comes with? They don't list the ounces so it seems like it wouldn't be all that much. Otherwise they would list how much it comes with.

thunderbearr · Post by **thunderbearr** » Tue Sep 13, 2005 2:23 pm

www.vagabondcorp.com also has samples available.

davehal9000 · Post by **davehal9000** » Tue Sep 13, 2005 4:27 pm

I posted a bit on ths a couple of days ago. I've tried casting on and off for almost 20 years, starting before it was commonplace using some odd materials. I haven't had much luck, normally getting a decent mold but very few usable casts.

A couple of years ago I started playing around with casting some Halloween props. I had problems with the casts looking OK, but being sticky and never drying. Someone recommended wiping them and the mold down with acetone, and it took care of the problem. I was using Mould Builder and fiberglass from Home Depot.

I'm currently working on a large studio scale model, and wanted to try to cast some parts to cut down on not so much the cost, but on the wasted kits. I picked up the Micro Mark set. My first couple of casts came out as usual, sticky. I wiped out the mold with acetone, and I've been getting perfect casts ever since. It seems to be the first 1 or 2 casts that have the problem.

In 2 weeks I've made more usable casts that I have in 20 years using other brands. Give Micro Mark a try. I think you'll be happy with the results.

Sparky · Post by **Sparky** » Tue Sep 13, 2005 4:58 pm

Be careful of the oomoo 30/25 series they mix pretty thick. I used a lot of it and sometimes you get a mold with few air bubbles and sometimes not.

There is some stuff that mechmonkey uses I have some mold he hand mixed without degassing. I think it is the alumilite brand rubber.

This stuff works great I have pressure cast his molds that where not degassed and did not damage the molds (which will happen with thicker RTV's that aren't degassed like what happened to my oomoo molds when I got the paint pot)

you can try the Moldmax series, don't worry about the measure by weight, I used the kitchen chef scale in the beginning and it worked fine. It may not be accurate for chemlabs but it worked fine for my moldmax 30. The mold max 30 has a longer cure time (longer pot life) and is runnier than the oomoo when mixed, so it's an option if you can't find the stuff mechmonkey uses. . .

Just stay away form the 15 minuet cure resins, they get so hot so fast they seriously reduce the life of your molds, might as well be pouring white metal! Also I've had a cup harden up on me, just not enough time to coax resin into a complex mold

bobbyfett · Post by **bobbyfett** » Wed Sep 14, 2005 10:27 pm

I've been leaning towards the MicroMark kit since it seems very complete, is very easy to order, and is only about $70. It's got about a half gallon of resin and rubber plus a bunch of other stuff. Anything bad about the MicroMark kit?
Is the MoldMax series from SmoothOn? I can't recall offhand as I don't remember seeing that name.

davehal9000 · Post by **davehal9000** » Wed Sep 14, 2005 10:39 pm

I like the Micro Mark stuff. I'm using a $2 kitchen scale from Wal Mart for measuring the mold material, and have had no problems. I use clear plastic, dixie-cup sized cups for mixing the resin. I eyeball the right proportions, and it works fine. Either I'm getting the hang of casting in general, or this is really easy stuff to use.

bobbyfett · Post by **bobbyfett** » Wed Sep 14, 2005 10:56 pm

I've heard that the MicroMark and SmoothOn stuff are the same thing. MM CR 300 is Smooth Cast SC 300 and 600 is 305. Any truth to this?

davehal9000 · Post by **davehal9000** » Thu Sep 15, 2005 12:07 am

I really couldn't tell you. I'd been so gun shy of putting the money out to try casting again, so I haven't tried much that was on the market.

Sparky · Post by **Sparky** » Thu Sep 15, 2005 8:28 am

bobbyfett wrote:I've been leaning towards the MicroMark kit since it seems very complete, is very easy to order, and is only about $70. It's got about a half gallon of resin and rubber plus a bunch of other stuff. Anything bad about the MicroMark kit?
Is the MoldMax series from SmoothOn? I can't recall offhand as I don't remember seeing that name.

Use moldmax is from smooth-on, its good stuff don't get put off by the mix by weight, a chef mate scale from target works fine. I use the bigger scale from American science and surplus so I can mix more at a time (scale goes to 1000 grams)

Blappy · Post by **Blappy** » Thu Sep 15, 2005 8:57 am

bobbyfett wrote:I've heard that the MicroMark and SmoothOn stuff are the same thing. MM CR 300 is Smooth Cast SC 300 and 600 is 305. Any truth to this?

This is indeed true.

The SmoothOn kits with the Mold Max Rubber give you two pounds of rubber. The resin they include is two pints.

I recommend the SC-305 resin as well because it gives 7 minutes to get the stuff into the molds. Its whats used here at BLAP! Models and gives us beautiful castings.

bobbyfett · Post by **bobbyfett** » Thu Sep 15, 2005 9:04 am

Ok, cool. That's good news. So since they are the same, is Alumilite similar? Or is it a totally different formulation? They say it is odorless. Is odor a problem with the MM/SO?

Blappy · Post by **Blappy** » Thu Sep 15, 2005 9:18 am

bobbyfett wrote:Ok, cool. That's good news. So since they are the same, is Alumilite similar? Or is it a totally different formulation? They say it is odorless. Is odor a problem with the MM/SO?

Alumilite is evil. It goes off REALLY fast and gets very hot. Its (literally) burns out molds quickly.

The Smooth-On stuff is pretty much odorless as well.

Sparky · Post by **Sparky** » Thu Sep 15, 2005 9:21 am

I've never noticed an odder with the moldmax rubber, could be my allergies are good for something. The 15 minuet resin I got from the hobby store, its Alumilte brand, did smell very strong. But I'll bet any brand's 15 minuet resins stink, since they are practically boiling hot as they cure. Don't use these, they seriously shorten your mold's life. Within 3 castings you'll see the rubber start to discolor. Man you can not expose rubber to heat

Sparky · Post by **Sparky** » Thu Sep 15, 2005 9:22 am

Wow you got in there as I was spell checking Blap.

bobbyfett · Post by **bobbyfett** » Thu Sep 15, 2005 9:40 am

Heat = Bad...got it!

So the 30 minute resins would be a good choice then? The MM600/SO305. It looks like I'm going to go with SmoothOn as they are a bit cheaper than MicroMark for the same matetrial, and they have larger quantities available. Thanks everyone!
Would this be a bad time to ask about rotational casting? It is possible to do this by hand, correct? Do I just slowly turn it over and over, shake it slowly, vigorously? Only turn on one axis? I'm a bit in the dark on that as well.

chasd25 · Post by **chasd25** » Fri Sep 16, 2005 12:34 pm

Regardless of the mold life, thickness of rubber......if you've never made any models before, the smooth on silicon sampler is a good (and CHEAP) introduction to the materials.

Some people HATE the OO MOO RTVs, and I'll admit, they aren't ideal for all appilcations. But they are a good introduction to the material. I keep some on hand for when I need a mold FAST, and only need a few castings out of it.

Micro Mart is Smooth on in different containers! (and a bit of a mark up I believe).

As for the pot life of resins.....yes heat = bad, but it all depends. Do you want 5 castings, or 50?

I've used the 3 min. potlife resin on for my Batman bust (uses about 16 Oz of resin), and got about 56 pulls before the mold went bad......

I've also blended some resins (within the same family) to alter the curing times. Mix a 3 min, with a 15 min to get something inbetween.....

Of course the best way to learn is to play with the stuff and figure out what works best for you.

My fav resins:

Smooth On 300, 325, 320
Vagabond
Douglas and Sturgess Insta-cast (white) (I use this about 80% of the time)
Synair Mk II por-a-cast

Charlie

bigjimslade · Post by **bigjimslade** » Thu Oct 13, 2005 8:10 pm

I have used Micromark and Smoothon resin and had good results with both. However, you can get a much better price deal ordering in bulk from Smoothon.

I was wondering if anyone knew of a build source equivalent of Micromark's 82083 1-to-1 mold rubber. It's rather pricy in their small packages. I never order one.

I've tried some of smoothon's two-part rubbers but never had any good sucess. Maybe just using the wrong type.

modelnutz · Post by **modelnutz** » Fri Oct 14, 2005 7:27 am

I'll second the recomendations for the Smooth-On materials.
I use Mold Max 40 all day long and it works great.
As for a very nice, mold friendly resin, you can't go wrong with SC-320
It kicks to a cream colored plastic and cures with a low temp.and is paint friendly as well.

Another trick you might try on your first cast is to heat the molds.
I warm my oven till hot ( 150 deg ) set the mold in keeping the door slightly open and wait 15 - 20 min. You want the molds warm, not super hot.
On a new mold this is almost required or else the first few pulls do not cure right......the molds draw the heat away from the plastic ( not good )
It's also a must do if the parts are very small ( something like a ladder type structure ) ;-)

This may be the cause of the "gummy" plastic mentioned previously.

Good luck and keep us posted with any problems and I'm sure you'll find all the help you need.

Modelnutz 8)
"the name sez it all"

bobbyfett · Post by **bobbyfett** » Fri Oct 14, 2005 2:02 pm

Well I went and got the MicroMark set. It's quite nice. The molds come out good and the first castings come out perfect if I use a little acetone on a Q-tip to clean them first. I asked MicroMark what the SmoothOn equivalent is but, not suprisingly, they won't tell me. The resin seems to be SmoothCast 305 and the rubber is OOMOO 30. I'm pretty happy with both. I wish the rubber was a little thinner though, as I had some trouble getting it into little tiny details. This was solved by brushing it into them first and then pouring.
I also stumbled on a neat way to make mold boxes using foamboard from WalMart. I don't need to use any glue or tape to seal my mold boxes and prevent leaks. It's really easy. I've outlined the technique on my page here: http://www.starwarsmodels.com/techscratch.html

chasd25 · Post by **chasd25** » Fri Oct 14, 2005 3:58 pm

Glad it worked out for you, now the next time you need some resin, get it straight from the source, and avoid that micro-mart markup!

Foam core is great stuff for mold boxes, I build boxes out of this stuff, and use hot glue to tack it all together. Works for about 90% of my molds!

Charlie

bobbyfett · Post by **bobbyfett** » Fri Oct 14, 2005 4:02 pm

Hey Charlie,
I plan on getting it from SmoothOn next time I need more. It was so funny getting the runaround from MicroMark technical assistance.

About the foamcore, I don't know if you read my method or not, but if you do it the way I do you don't even need hot glue.

It's soo easy. And it saves having to use glue. 8)

jack wendt · Post by **jack wendt** » Fri Oct 14, 2005 9:57 pm

bobbyfett wrote: Would this be a bad time to ask about rotational casting? It is possible to do this by hand, correct? Do I just slowly turn it over and over, shake it slowly, vigorously? Only turn on one axis? I'm a bit in the dark on that as well.

never tried roto casting, but have seen it done at a smoothon seminar offered by reynolds advance products in houston texas. they are the distributer for smoothon in texas. i can order a trial size on monday and have it by the next day, or one day later by ups.

the mold naturally has a cork. it is spent on a machine on all 3 axis. this is done slowly so as not to introduce bubbles to the resin.

i have never tried it, but in theory it could be done by hand.

i have done slush casting with excellant results. slush casting is simply gently rocking the resin to all the sides of an open face mold.

the actually machine will act like the contraption that the pod that jodie fostor was in, is dropped thru in the movie contact. you know the 2 or 3 rotating rings. same principle.

beside having a hollow interior, you use less than half the resin, or there abouts.

as for heating the molds, i was informed in the smoothon class that heating the rubber will bring fresh silicon to the surface extending the life of the mold.

as i said on other occasions, with the oomoo rubber, be sure to use the mann 800 mold release. there may be substitues such as talcum, but this is what i was taught in the seminar, and this is what i use. one can has lasted about 3 years i reckon.

bobbyfett · Post by **bobbyfett** » Mon Oct 31, 2005 9:58 am

Want a good laugh? I need more rubber and was planning to get the two gallon kit from SmoothOn. I figured I might as well e-mail MicroMark to see if they can match or beat the price and I get an auto response back saying I am "blocked for abuse". I guess nowadays abuse means asking questions they don't want you to ask.

I wasn't even the slightest bit rude or belligerent or anything like that. Too bad for them, now I am definitely buying from SmoothOn.
Anyway, back on the subject, the Oomoo has worked out great for me so far. The 1-1 mix is super easy and it captures all the detail I need. I'm going to try some hand rotational casting once I get more rubber.

unsc shipworks · Post by **unsc shipworks** » Sun Nov 06, 2005 11:36 pm

davehal9000 wrote: I'm currently working on a large studio scale model, and wanted to try to cast some parts to cut down on not so much the cost, but on the wasted kits. I picked up the Micro Mark set. My first couple of casts came out as usual, sticky. I wiped out the mold with acetone, and I've been getting perfect casts ever since. It seems to be the first 1 or 2 casts that have the problem.

I had similar experiences, but then I found if I let the mold stand for at least 24 hours after removing the master part then it didn't give me any problems with sticky casts.

Blappy · Post by **Blappy** » Mon Nov 07, 2005 1:20 am

unsc shipworks wrote:
davehal9000 wrote: I'm currently working on a large studio scale model, and wanted to try to cast some parts to cut down on not so much the cost, but on the wasted kits. I picked up the Micro Mark set. My first couple of casts came out as usual, sticky. I wiped out the mold with acetone, and I've been getting perfect casts ever since. It seems to be the first 1 or 2 casts that have the problem.
I had similar experiences, but then I found if I let the mold stand for at least 24 hours after removing the master part then it didn't give me any problems with sticky casts.

The problem here is you are not letting the mold cure enough before casting in it. I use the Smooth-on Mold Max-40 and I find I need to leave the molds open to the air for about 24 houtrs before I cast. What is happening is the Alcohol is not evapourating off and giving you sticky casts. The alcohol is part of the curing process. You can accelerate this by baking the molds but I find its easier to just wait a day to cast.

bobbyfett · Post by **bobbyfett** » Mon Nov 07, 2005 7:57 am

Do you guys think it is best to store the master parts in the molds to help the molds keep their shape and to help protect the master parts? Is this a good idea?

Blappy · Post by **Blappy** » Mon Nov 07, 2005 9:31 am

bobbyfett wrote:Do you guys think it is best to store the master parts in the molds to help the molds keep their shape and to help protect the master parts? Is this a good idea?

I don;t think so. You will never get themaster back into the mold 100%. AAny small projections or scribbed lines will never go back into the original grooves in the master.

I keep all masters stored safely in bubblewrap and whatever it needs to prevent damage.

The molds are all stored flat in large "tupperware" type containers. I have diffferent containers for different customers.

rocketrider · Post by **rocketrider** » Mon Nov 07, 2005 3:45 pm

bobbyfett wrote:I also stumbled on a neat way to make mold boxes using foamboard from WalMart. I don't need to use any glue or tape to seal my mold boxes and prevent leaks. It's really easy.

Ive seen others use Legos to create mold boxes as well, nice thing about them is that they go together quick.

Glen

Starship Modeler Discussion Forums

Resin & RTV: MicroMark, SmoothOn, Polytek or Alumilite?

Resin & RTV: MicroMark, SmoothOn, Polytek or Alumilite?

Rubber Source