Urethane Casting Question

[harzzle]

So after semi-successfully pulling a latex batman cowl this week from a plaster of paris mold, I am looking to use what I learned the first time around to give casting a urethane cowl a go.

My question is: Is it a good idea to cast the urethane in an ultracal 30 mold and if so, is petrolium jelly a good release agent for the two materials?

I am trying to do this as cheaply as possible which is why I am choosing ultracal over silicone or any other mold materials (As well as the fact that I am familiar with making plaster molds).

 

[RokkaRolla]

Hello, well it really depends on the type/brand of urethane your using (how soft/rigid/flexible will it be?). Ultracal 30 is great for molding, I use it all the time for latex & silicone castings, and it's way more durable than plaster of paris. If it's a soft-flexible type of urethane, then an ultracal 30 mold should be good, but if it's gonna be a rigid cast, you'll need a soft, flexible mold, like silicone. Personally, I avoid petroleum jelly with anything, as it may interfere with the curing process (again, that really depends on the type of casting material). The best thing is to do some small test pieces, a good habit which I myself am guilty of neglecting. Smooth-on makes good products, but I buy a lot of materials from industrialpolymers.com, because they give you more for your money. Hope this helps, sorry if I just gave you an earful of what you probably already know

 

[harzzle]

Hello, well it really depends on the type/brand of urethane your using (how soft/rigid/flexible will it be?). Ultracal 30 is great for molding, I use it all the time for latex & silicone castings, and it's way more durable than plaster of paris. If it's a soft-flexible type of urethane, then an ultracal 30 mold should be good, but if it's gonna be a rigid cast, you'll need a soft, flexible mold, like silicone. Personally, I avoid petroleum jelly with anything, as it may interfere with the curing process (again, that really depends on the type of casting material). The best thing is to do some small test pieces, a good habit which I myself am guilty of neglecting. Smooth-on makes good products, but I buy a lot of materials from industrialpolymers.com, because they give you more for your money. Hope this helps, sorry if I just gave you an earful of what you probably already know

No that is all VERY helpful thank you! The type of urethane I'm looking to use is shore A45 as most people here seem to use A40. I can only get my hands on 45 as my options here in NZ are fairly limited. I basically only have access to a website call topmark.co.nz for my materials and it can be difficult to pick which products to use from their selection. Can petroleum jelly have a bad effect on urethane?

 

[RokkaRolla]

Whoa, you're from NZ, I hope I'm not giving you bad advice (I'm from the U.S., and latex seems to be the more popular choice here than it is over there). I really wish I had more experience with urethane, which seems to be the drink of choice in Europe and other countries. I know that most people cast urethane in silicone molds, which do not require any release agents (because nothing sticks to silicone). Over here, a shore a-45 hardness is fairly rigid, which can be pretty hard for a plaster mold. I hate to see the details in your mold chip off/crack when you pull out the casting, especially if you need to do multiple casts. Just be sure to use a delicate touch!
As for petroleum jelly, I honestly am not sure, you might have to experiment. But if I had to take a wild guess, I'd say that it's probably not good, since it will mix with the liquid urethane & could counter-act the curing process (it might not cure at all, or come out "goopy"), which would ruin all that work you've done. Your best bet would be to contact the seller or manufacturer, as they tend to know more about the stats of their products. In fact, I would ask which of their products would work best for your mold, they might have an alternate solution to urethane.
Again, hope this was at least a bit helpful. Post some pics if it works out!

 

[clonesix]

There is only one reason that this couldn't be done, and that the fact that Urethane without release is GLUE, and plaster of paris is porous and soft. Not a good combination.

but a good seal of the plaster and a heavy coat of release would allow you to get a urethane cowl out of the mold. It would also ruin the mold for latex, and could just ruin the mold if the urethane didn't release well.

If you want cheap, stay with latex. My $0.02

 

[RokkaRolla]

There is only one reason that this couldn't be done, and that the fact that Urethane without release is GLUE, and plaster of paris is porous and soft. Not a good combination.

but a good seal of the plaster and a heavy coat of release would allow you to get a urethane cowl out of the mold. It would also ruin the mold for latex, and could just ruin the mold if the urethane didn't release well.

If you want cheap, stay with latex. My $0.02

Oh, by no means did I mean to imply NOT using a release agent; I just have my doubts about petroleum jelly. I agree 100% about the latex, it's always been my drug of choice

 

[RokkaRolla]

Hey Harzzle, hope I'm not giving you a headache. I did some checking around (as I implied earlier, my experience with urethanes is limited). You would definitely need a release agent, but petroleum jelly is a no-no; I have found that petroleum-based products can and will likely ruin the outer skin of most castings, and as I said before, you'll end up with goop (unless you find a specific product that works with this). Also, all my sources tell me that a plaster mold is not the best idea for a urethane casting. If anything like this exists, maybe you could find a silicone-based release agent. If I was in your place, I'd re-mold the whole thing with silicone. Otherwise, latex would be the best option for casting, as clonesix suggested. Good luck!

 

[FXGuy]

I was slated to work on a film in Columbia back in the mid 1990s and the budget allowed me to ship some things over- seeing as there was no guarantee what would be available once we were in-country...

I selected a 2-part urethane [cold cure] BJB TC264 that allowed for a two gallon "Part B" and a single 1 quart bottle of "Part A" to travel: it took up a lot less space and a lot less weight!

Now- that said, BJB Enterprises uses a "hardness" scale to base their numbers- a 264 rating being it's "hardness"- example: BJB Enterprise's TC 892 is considered a "Rigid" that sets more like an automobile armrest- 264 is quite pliable.

The agent used for "release" [hence "release agent" *ahem* :lol] was a WAX-type product much like today's Finish Kare 1000L-28 which can be airbrushed or simply painted into your mold- I used Ultra-Cal molds which have a similar poracity [is that even a word?!] as a plaster of paris- but the material is actually used in concrete drive repairs!

As stated earlier- urethanes are more like "glues" while they cure- so a release agent is ULTRA important [learned the hard way once! By using a "wax" [they all have a little bit of silicone in their mixes now- but not back in the 1990s] 3 fine coats of agent [yes- THREE] will still keep your finer details visible when you make your mask pulls.

I can fill you in on my uses of urethanes- though it's been limited to relatively "simple" prosthetic pulls but urethane uses tend to need both a positive and negative mold to make the urethane "behave" and flow whee yo want it to go!

Hope this helps! :thumbsup

 

[RokkaRolla]

I was slated to work on a film in Columbia back in the mid 1990s and the budget allowed me to ship some things over- seeing as there was no guarantee what would be available once we were in-country...

I selected a 2-part urethane [cold cure] BJB TC264 that allowed for a two gallon "Part B" and a single 1 quart bottle of "Part A" to travel: it took up a lot less space and a lot less weight!

Now- that said, BJB Enterprises uses a "hardness" scale to base their numbers- a 264 rating being it's "hardness"- example: BJB Enterprise's TC 892 is considered a "Rigid" that sets more like an automobile armrest- 264 is quite pliable.

The agent used for "release" [hence "release agent" *ahem* :lol] was a WAX-type product much like today's Finish Kare 1000L-28 which can be airbrushed or simply painted into your mold- I used Ultra-Cal molds which have a similar poracity [is that even a word?!] as a plaster of paris- but the material is actually used in concrete drive repairs!

As stated earlier- urethanes are more like "glues" while they cure- so a release agent is ULTRA important [learned the hard way once! By using a "wax" [they all have a little bit of silicone in their mixes now- but not back in the 1990s] 3 fine coats of agent [yes- THREE] will still keep your finer details visible when you make your mask pulls.

I can fill you in on my uses of urethanes- though it's been limited to relatively "simple" prosthetic pulls but urethane uses tend to need both a positive and negative mold to make the urethane "behave" and flow whee yo want it to go!

Hope this helps! :thumbsup

I can't speak for Harzzle, but this has been a great help to me! My background is more solid with foam & liquid latex, silicones, and resins than with urethanes, so I'll take whatever knowledge I can grab. Thanks! And yeah, the wax thing is right (how'd that slip my mind... it's been years since I touched urethanes). Nothing like being rusty

 

[harzzle]

Everybody has been incredibly helpful! Thank you all so much

As this is only the second time that I've delved into molding and casting, I might just keep to latex for this one. I will definitely be switching from plaster of paris to ultracal now but for the price of urethane materials that I will most likely end up ruining during the learning process, it just won't be worth it.

Does anybody know if there is something out there that I could add to latex before casting that would increase the hardness of the final mask? I'm just looking for a flexible but really solid looking result which is why I was looking into urethanes to start with.

 

[RokkaRolla]

I believe they do make thickening agents for latex (search for "latex thixotropic agents"), but I've never used them. It also depends on who manufactures the latex you'll buy; I've used some that come out more firm than others, and also, using several coats will make it thicker too. The Monster Makers (Ohio, U.S.A.) makes a pretty thick latex that I use a lot

 

[Scuba Bob]

I second RokkaRolla. Monster Makers RD 407 latex is second to none. I've used a lot of latex compounds out there and the RD 407 is amazing. It is very stretchy but very strong. If you're going to stick with latex, i'd recommend hydrocal as your molding material. plaster of paris is good but can crack apart in the demolding process and ruin all of your hard work. Hydrocal is also very easy to work with and you can build up a full 2 part mold very quickly. If you're looking for a thick, tough mask. I'd get a large bucket of latex (i always buy the 5 gallons) and pour it into your plaster mold and fill to the top. Let that "dwell" for about an hour and then pour the excess back into your bucket. let the skin dry and you will have a durable, solid mask that will last for a long time. a 5 gallon bucket should last you in the neighborhood of 15-20 masks depending on their size.

I'd stay away from using a thixotropic agent in latex as it might make the latex too thick to capture all of the detail in your mold. if you're rotocasting with latex, you want it to be pretty thin. When i do this process, i add in some distilled water to thin out the latex (dont worry the extra water will be drawn into the stone mold during the curing process). To speed up curing you could also use a spray bottle full of vinegar and wet down the mold with it and it will speed the latex drying.

 

[harzzle]

I second RokkaRolla. Monster Makers RD 407 latex is second to none. I've used a lot of latex compounds out there and the RD 407 is amazing. It is very stretchy but very strong. If you're going to stick with latex, i'd recommend hydrocal as your molding material. plaster of paris is good but can crack apart in the demolding process and ruin all of your hard work. Hydrocal is also very easy to work with and you can build up a full 2 part mold very quickly. If you're looking for a thick, tough mask. I'd get a large bucket of latex (i always buy the 5 gallons) and pour it into your plaster mold and fill to the top. Let that "dwell" for about an hour and then pour the excess back into your bucket. let the skin dry and you will have a durable, solid mask that will last for a long time. a 5 gallon bucket should last you in the neighborhood of 15-20 masks depending on their size.

I'd stay away from using a thixotropic agent in latex as it might make the latex too thick to capture all of the detail in your mold. if you're rotocasting with latex, you want it to be pretty thin. When i do this process, i add in some distilled water to thin out the latex (dont worry the extra water will be drawn into the stone mold during the curing process). To speed up curing you could also use a spray bottle full of vinegar and wet down the mold with it and it will speed the latex drying.

I would love to get one of the monster makers kits but unfortunately it's way too expensive to ship to New Zealand and I can't get the latex on it's own because the minimum price for international shipping is $200 :cry

What's the difference between hydrocal and ultracal? The price is the same at the place i can get the two but I've noticed people like to use either one or the other.

This might be a bit of a stupid question but do you spray the vinegar on the inside of the mold before pouring the latex or on the outside after pouring the latex?

 

[harzzle]

I also just wanted to say a massive thank you to everybody for all the amazing advice! You're all helping me learn so much and I really appreciate it

Cheers!

 

[RokkaRolla]

I second RokkaRolla. Monster Makers RD 407 latex is second to none. I've used a lot of latex compounds out there and the RD 407 is amazing. It is very stretchy but very strong. If you're going to stick with latex, i'd recommend hydrocal as your molding material. plaster of paris is good but can crack apart in the demolding process and ruin all of your hard work. Hydrocal is also very easy to work with and you can build up a full 2 part mold very quickly. If you're looking for a thick, tough mask. I'd get a large bucket of latex (i always buy the 5 gallons) and pour it into your plaster mold and fill to the top. Let that "dwell" for about an hour and then pour the excess back into your bucket. let the skin dry and you will have a durable, solid mask that will last for a long time. a 5 gallon bucket should last you in the neighborhood of 15-20 masks depending on their size.

I'd stay away from using a thixotropic agent in latex as it might make the latex too thick to capture all of the detail in your mold. if you're rotocasting with latex, you want it to be pretty thin. When i do this process, i add in some distilled water to thin out the latex (dont worry the extra water will be drawn into the stone mold during the curing process). To speed up curing you could also use a spray bottle full of vinegar and wet down the mold with it and it will speed the latex drying.

Damn, I'm gonna try the vinegar thing! Amazing that an old fart like me can still learn stuff. I also like to get the 5 gallon buckets, you get more for your money!

 

[Scuba Bob]

I would love to get one of the monster makers kits but unfortunately it's way too expensive to ship to New Zealand and I can't get the latex on it's own because the minimum price for international shipping is $200 :cry

What's the difference between hydrocal and ultracal? The price is the same at the place i can get the two but I've noticed people like to use either one or the other.

This might be a bit of a stupid question but do you spray the vinegar on the inside of the mold before pouring the latex or on the outside after pouring the latex?

Hydrocal is a plaster, ultracal is a gypsum cement. Hydrocal is more absorbant for latex applications. Hydrocal is also mixed as one batch and thickens as you go along with it. When i make a hydrocal mold i will mix up a big batch of it to the consistency of milk. I will brush on my detail coats and as i'm doing that the hydrocal will begin to gel and thicken. As it does that i will put a nice thick layer of the gelled hydrocal on and then begin laying up with my reinforcing material (burlap or fiberglass mat). As it begins to harden i will rub it down with a piece of burlap to smooth it out for a nice pretty mold. With ultracal, you have to mix seperate batches. You will do 1 batch for your detail coat and let dry, do another thicker for your 2nd coat, let dry, do another for your reinforcement, let dry etc... it takes a while but is a harder more durable mold. Personally if i need a durable solid mold i will use epoxamite and epoxacoat from smooth on and make an epoxy resin mold.

Spray the vinegar into the mold before pouring the latex. I only do this when trying to cast latex into a resin or silicone mold where the water wont be absorbed. If you're using hydrocal and doing a pour and dwell technique, you will find an amazingly thick skin within an hour.

 

[RokkaRolla]

Yeah, Scuba Bob definitely know what he's talking about. I personally like ultracal the best, because of the longer working time. Hydrocal is great, but it sets up very quickly & I've had it gel too fast for me. You gotta be quick with that stuff if you ever do big molds! Plus Ultracal is more chip-resistant than hydrocal, but hydrocal tends to be cheaper. Sorry about the shipping dilema, that sucks!

 

[Ozymandius]

I know I'm a bit late to the party here but you can definitely cast urethane rubbers into plaster molds with great success. However wax as a release agent is only half the equation. You also would need to coat the mold with PVA. Otherwise the heat from the urethane will burn off the wax and it will be bonded to the plaster.

The good thing is that both wax and PVA are both stupid cheap and easy to use.

PVA (Poly Vinyl Alcohol) is basically a plastic suspended in an alcohol solution. It is brushed into the mold and then allowed to dry until all the alcohol has evaporated out. What you are left with is a very thin plastic barrier that protects your plaster. I would recommend 3 or 4 coats for safety and make sure you coat the seams of the mold as well. After the PVA layer is done, you can then brush on your wax and cast safely.

Now here's the bonus. PVA does not soak into the plaster and can be washed out so that the mold can still be used with latex later if you want. In fact, most of the PVA should peel off when you demold and will have to be reapplied for every casting.

The PVA and wax method works with urethane rubbers, foams, and even plastics if you don't have any undercuts and I've run molds with all three of them.

 

[BlackKaos]

I hate to jump in on this thread and asked a question myself but it seamed more logical to ask her then make my own thread for a question.

Can anyone help answer this for me. I am planning on making my own Bane mask from a pep file that I created. The mask is going to be sculpted with multi different media and the finished product will be used for molding. I want to make a cast of the mask out of 40 shore urethane rubber.

My question is what would be the best material for making mold if I was going to cast 40 shore urethane rubber? Would a Silicone mold work with Urethane rubber?

 

[Ozymandius]

Yes, silicone would be an ideal mold to cast urethane rubber.