My second attempt to cast anything- NEED HELP!!!

Richard Baker · Post by **Richard Baker** » Tue Mar 31, 2009 7:54 pm

Below is a casting of the Reactor Wall from the Moebius Flying Sub (to go on the port side)
http://i41.photobucket.com/albums/e267/ ... 0055-1.jpg
First time I tried to cast something.

Yea!

Details of current problem in lower post

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Stu Pidasso · Post by **Stu Pidasso** » Tue Mar 31, 2009 8:33 pm

Beginner's luck!

Richard Baker · Post by **Richard Baker** » Tue Mar 31, 2009 8:36 pm

I am not picky- I will accept ANY kind of luck these days...

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photoguy · Post by **photoguy** » Tue Mar 31, 2009 9:09 pm

That looks pretty dag-gone nice!

what materials did you use?
Alumalite?
Oomoo?

Richard Baker · Post by **Richard Baker** » Tue Mar 31, 2009 9:29 pm

Nothing fancy-
EasyCast clear casting epoxy.
The mold was from brushed on latex mold builder (many layers)

I know there are much better materials and methods but I just needed to make this one part for my project. Now that I know it is so much fun I will get more ambitious for the next one.

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Richard Baker · Post by **Richard Baker** » Fri Apr 10, 2009 6:51 pm

HELP!
OK- I screwed up- the question is how badly. My second attempt for a mold I went with Alumilite Silicone. Mixed it to a perfect 1 to 10 ratio, used a set of Legos for the mold box. I was doing a one sided mold so I just poured the compound, placed the piece into the top nd held it down with more lego fingers until the next day.
Perfect mold- nice even color, firm- I really like this silicone over the latex I used the first time.
My new piece needed to be clear also so I mixed the EasyCast clear casting epoxy.
Here is where I screwed up- I forgot to use any mold release. I poured the material straight into the mold and let it set 24 hours.
The casting did release from the mold OK- no problem popping it loose since it is a flat control panel. The problem is that the casting material seems to have had a reaction to the silicone rubber- it is a hard perfect casting until you get to where the mold was in contact with it- it is 'sticky'. Bother mold and the casting have a sticky surface though good detail.
Is the mold OK? Can it be cleaned and with what? I would still like to use this casting epoxy I have- would a PAM or mold release prevent a reaction?
I do have some unopened Alumilite 'Super Plastic' resin- it does not say if it is clear or translucent/opaque. I am making back lit control panels with lots of detail- I need it to be clear.

Any help or suggestions will be greatly appreciated!

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modelnutz · Post by **modelnutz** » Fri Apr 10, 2009 7:05 pm

You may have better luck if you heat the mold first.
E-Poxy is a catlyzed reaction...meaning that it requires heat to cure correctly.
Silicone is a real good heat sink.

Another issue could be alcohol leaching from the silicone...but this typically makes for a cloudy casting.
Heating the mold in an oven set at 180 degrees for about a half hour may do the trick.
You can also pre-heat your E-Poxy resin ( heat the 2 parts seperatly ) then mix and pour...but remember, the hotter resin will cure faster.

If you still have issues..PM me, I can help.

Richard Baker · Post by **Richard Baker** » Fri Apr 10, 2009 7:18 pm

Is the mold salvagable or do I need to scrap it and make a new one?

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modelnutz · Post by **modelnutz** » Fri Apr 10, 2009 8:09 pm

Take some of you regular resin and pull a cast of two from the mold...that should pull all the gunk from the mold.

Joseph Osborn · Post by **Joseph Osborn** » Fri Apr 10, 2009 8:15 pm

Modelnutz hit the answer-- excess alcohol leaching from the tin-cure silicone. If you don't post cure the mold for about 4 or 5 hours at 125F, then you'll get a putzy first pull. Did you use the "quick set" or the "high strength" silicone? I remember that quick set stuff is particularly nasty when it comes to the alcohol leaching.

You should be able to clean the residue out of the mold with some acetone and go at it again.

Also, regular Alumilite resin cures to a creamy yellow opaque plastic.

macfrank · Post by **macfrank** » Fri Apr 10, 2009 8:36 pm

It sounds like the reaction I had with Envirotex and RTV molds. Oomoo molds should work.

Richard Baker · Post by **Richard Baker** » Fri Apr 10, 2009 8:48 pm

I used the Alumilite 'Quick Set' RTV mold and cured for 24 hours before using (the frakk'n instructions never mentioned anything about heat).
I wll get some acetone tomorrow and try to get it cleaned up- I do not have a lot of materials to work with here so I would rather not waste some of the casting epoxy for a cleaning pull or remake the mold if I can help it.
So - I get some acetone and a soft cloth and wipe aray until the stickyness is gone. Since the putzy first pull is over with would it be OK to trat the mold with PAM and then try to pour a second clear Epoxy cast? I don't want to nickel & dime too much, but running a gas oven for 4-5 hours with just a piece of rubber in it is going to make AlaGasCo very rich. I am hoping the PAM would act like a barrier.
If this was a big kit set of molds it would be one thing, but I am casting a flat unit about 1 1/2"x2" (a wall control panel from the Moebius Flying Sub). I just need two casting for now and one more mold from the back wall. Some people over at the Hobbytalk forum have contacted me regarding trying to get a set of these for their build, but since I have not heard back from Moebius about ti (I would be dupluicating their exact part, but just making an accessory) any furhter castings are conjectural for now. If I do get a nod to proceed and some ordders, I will make some new molds with all the fancy heat treatments.

EDIT (posted while I was typing above)

Oomoo molds should work

What is an Oomoo mold?
My castings are coming out water clear (not yellowed like in your linked thread) but both are sticky. I do have the Alumilite casting resin also, but the whole point of this is to create clear replicas of the kit parts for backlighting. I owuld like to just get the three parts I need for now using wht I have already purchased. Later down th eline (next month or so) I am going to begin casting detail parts fo rothers, but this time I am just on a learning curve for my own builds.
This is a fun thing, but getting aggravating.

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macfrank · Post by **macfrank** » Fri Apr 10, 2009 8:58 pm

Richard Baker wrote:
EDIT (posted while I was typing above)
Oomoo molds should work
What is an Oomoo mold?
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It's a 2 part, 1:1 mix made by Smooth-on. If you have a Dick Blick art store (or similar - not Michael's, though - they're useless) they may carry it. If not, order it from Smooth-on or Msterart or The Compleat Sculptor.

Acetone probably won't work without (later) heating the mold to cook the crap out of it, and the clear resin will never stop being soft and sticky. Read the link in the construction section.
Casting in clear can be a PITA. Alumilite makes a clear resin that'll work in their molds, but it sets so quickly that you'll end up with bubbles. It also needs to set in a warm mold.

While not a resin - and expensive and stinky - nail/dental acrylic will work and if the part isn't very thick, can be cast very clear. A small bottle good for maybe 1" x1" x 1/4" will set you back about $8.

Frank

Richard Baker · Post by **Richard Baker** » Fri Apr 10, 2009 9:27 pm

Well it looks like I am going to have to go back to making a Latex mold for this current project. I do not have the funds to get a bunch of new materials just for a three castings. I will deal with making some new silicone molds and baking hem IF there are going to be additioanl casting fo rothers, but that is uncertain right now.
Those are some great supply site you linked me to. Birmingham does not have a source for those products, Michaels & Hobby Lobby are just about it. The other Art supply sotres do not deal with molding/sculpture- mostly flat art like paintings and pastels.
I already have this stuff and I am in a negative cash flow so I cannot go on line and buy anything else right now. I do have almost a quart of Latex and several packages of the 28oz Alumilite resin (opaque) and a cup and a half of the clear cast epoxy. I will have to make do with that for now. When things are better off financially and I get rolling on future projects I will revisit this again.

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Lt. Z0mBe · Post by **Lt. Z0mBe** » Fri Apr 10, 2009 10:10 pm

With the latex, make MANY thin coats, instead of large ones. Also, make sure you work it into the recesses. Thin the first coat just a bit with distilled water to facilitate that.

Dry your layers in a food dryer or, what I did, you wife's hair dryer in a clamp.

I hope this helps.

Kenny

Richard Baker · Post by **Richard Baker** » Sat Apr 11, 2009 7:20 am

It does take a lot of thin coats to build up a stable mold- my first one took a week. I am letting them airdry for half a day or so- I won't add aanother coat until the curent one loses it's "white". Pollon season is finally past so I can set them in the sun- I am not in a big hurry so mechanical augmentation ofr drying won't be needed.
Thanks fro all your help guys! Casting is a new world to me and the chemistry problems are numerous. I will continue to experiment with th eSilicon molds and Alumilite resin for some other projects- I need to scratch & duplicate some parts for my 'To The Moon' entry where opaque will not matter.

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Stu Pidasso · Post by **Stu Pidasso** » Sat Apr 11, 2009 3:19 pm

Richard Baker wrote:Casting is a new world to me and the chemistry problems are numerous.

Y'all remember that next time you scream "IS IT READY YET???" for your kits..

Richard Baker · Post by **Richard Baker** » Sat Apr 11, 2009 3:59 pm

Y'all remember that next time you scream "IS IT READY YET???" for your kits..

I believe if you check back I was one of the very few who did pull the "IS IT READY YET???" routines. I got rid of that when I realized that the kits I bought on first day of issue aer still unbuilt after a year or so- between life and other projects in line my big concern is missing out on some of the low volume kits.

and I am still hoping that a set of landing gear for the Clone Troop Transport may eventually get created...

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macfrank · Post by **macfrank** » Sat Apr 11, 2009 4:00 pm

Richard, I haven't tried it, but... after putting a few layers of latex over the master and letting it dry, you may want to try a 1/2" of Alumilite RTV on top of that. It would give the latex mold some stiffness and the latex would act as a barrier between the RTV and the clear epoxy.

Frank

Richard Baker · Post by **Richard Baker** » Sat Apr 11, 2009 4:09 pm

I like that idea!
It should work if the latex and silicon play well together. I have the first latex coat dry, I will add a second layer of latex and then try the silicon instead of the third coat..

Stu Pidasso · Post by **Stu Pidasso** » Sat Apr 11, 2009 5:47 pm

Richard Baker wrote: I am still hoping that a set of landing gear for the Clone Troop Transport may eventually get created...

Evil ideas are abound. Be patient...