Casting a Complex Shape In A One Piece Silicone Rubber Mold 

Could you use 3D printed objects instead of wax? And could an object be a tad more complex and still work? Thankyou :)

Thanks!

Thanks so much for watching! I don’t have any grandkids - yet! 😊🥰

@@RobertTolone you have us 😁

Glad you found it useful. Thanks!

Thanks Mario. Feel free to suggest topics or share issues or problems you have with your projects. It really helps me to create content for the channel.

@@RobertTolone I've always wondered how you can make a doll head much like a Barbie doll or soft G.I. Joe head. Can't seem to find any info about it online. That would be awesome my friend. You should set up a Patreon if you haven't already.

Thanks Juan!

Great to hear your molds all came out well! Thanks for watching and commenting!

Thanks Tunc!

I appreciate that Filipe! Thanks.

Thank you! Cheers!

Thanks James, glad you found it helpful.

I’ve also used velcro for large molds. And bungees.

I appreciate that you watch and commented. Thanks so much!

Thanks Kiri!

Yes, it’s hard to pour rubber and resin at that temperature !

I appreciate your comment, thanks for watching!

Thanks Tim!

Learned to much in these videos. Can see the channel grow super fast as I go through different videos. Q: Do you know if you would be able to use this mold to pour soy wax in it and get at least 20-30 pieces out of it?

@@Virrba I have never heard of waxes wearing out silicone molds. We cast our sculpting wax, which is a mixture of beeswax, paraffin and carnauba wax, into silicon molds all the time without harming the molds at all. So I would expect to get a large number of sox wax castings out of a mold. The silicone should be able to tolerate the temperature of the melted wax easy enough. But if you have any doubts you could always use a high temperature silicone suitable for casting metals like pewter. I am not a candle maker and have never cast soy wax so maybe I am Ignorant of some property it has that could harm silicone.

@@RobertTolone I really appreciate your thoughtful reply. That sounds great. Will go and research any potential problem. Also, I think people would benefit if in the future you would review some pressure or vacuum chambers as the one in your studio looks large and intimidating and seems like people would not be able to afford that system but there are those under 100£ in UK that can be purchased from ebay. Your opinion on those would be valuable I believe.

Glad you liked it, thanks for letting me know.

I always stretch the silicone to cut it. That makes it much easier. Sounds to me like your cuts aren’t locking together enough. The cuts should be jagged but it doesn’t have to be crazy jagged. Where the cut meets the model the line should be a straight as possible. The harder the rubber is the more difficult it is to cut. I mostly use Shore A 25 rubber.

Thanks for watching.

Glad you liked it. Thanks for watching!

Reference book and video courses are in the works. I did a video on my pressure pots: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-VYO318KFuAA.html People often modify spray paint pots to use for casting resin

@@RobertTolone Fantastic, I look forward to reading your book when it comes out, and hopefully taking a course or two as well. Nifty stuff. Thank you for the pointer about the spray paint pots, and for the video link. Gonna watch that now! Stay awesome!

Thanks Mark. Good luck with your projects! Let me know if you have any questions about your molds.

@@RobertTolone Thank you for your reply, and I have a million questions :-) However.. my first one is what the Heck was that model you casted ?? I can't stop thinking about it's Nightmarish Shape LOL xx

Just a backlash from a career spent sculpting Disney, Looney Tunes , Nickelodeon , Sesame Street, etc toys. Too much of that and you spiral into the darkness.

@@RobertTolone HaHa I see .. Well I can put a name to it now.. Thank you for your Reply, I am watching your videos with surgical Observance(thats a word :-) and I am learning so much xx

Mark Cunningham I’m happy to be of help. Thanks.

Every shape is different so there really is only one rule when placing vents. I place my sprue so it attaches to the casting where it will be easy to clean up. The sprue should be large enough to allow a rapid flow of resin down into the cavity. If you make the sprue too small the resin will begin to set before the cavity is filled. If you make it too big you will waste effort on a big cleanup job.The resin flows from the sprue into the mold cavity and falls to the bottom. As it rises it push the air out above it. You need a vent anywhere that air can get trapped by the rising resin. Look for high spots; that’s usually where you need a vent.

I cut them off and carve them to match the surrounding surfaces as soon as possible after the casting comes out of the mold. The resin is much easier to work then. After trimming I simply use sandpaper in progressively finer grits to clean the part. This works well for urethane resins but I can’t see why it wouldn’t work for polyester.

@@RobertTolone Ahhhh I see, makes sense. I got to trim mine after a while which left it kinda hard and difficult to trim. Thanks for this!

Keep watching my channel! 🙂 Pretty much every video I make is about how I plan my sprues, vents and cuts. 👍

@@RobertTolone Okidokey👍

It’s a sculpture I did a couple years ago for fun. I used it for this video because it was challenging to mold and cast. I wanted to show viewers that one-piece cut molds can be used to cast complex models.

@@RobertTolone The sculpture looks like a sort of homunculus only with insect like eyes

@@richwojehowski1123 Everything I sculpt is a self portrait of how I feel, not how I look.

I do not put a rubber mold which has been poured around a model in the vacuum chamber for several reasons. First, it’s not necessary. If there are problems areas where air is likely to be trapped they should be pre-filled before the mold is poured. Otherwise, if the mold is poured properly and the rubber rises from the bottom and pushes the air out it will not trap any air. Second, I often make molds for people and I am not certain of the construction of the model. If there are any voids or air pockets inside the model they could explode or expand enough to damage the model. This is particularly true with clay models which very often have trapped bubbles inside them. And third, it’s hard to predict exactly how much the rubber will expand. So you have to make the case considerably bigger than necessary to allow for the expansion. It just isn’t worth the effort.

@@RobertTolone thanks for the explanations. I didn't think about "imprisoned" air in the original model.

@@jeromedesalle6973 I learned that the hard way when I destroyed a client job, an intricate little ship model. 😭. Never occurred to me it was hollow!

I don’t know if a crock pot can work; I have no experience with this. The pressure pots that I use were fabricated from the brake cylinders of large trucks and were made by a welder certified to do pressure vessels. A poorly made pressure pot could be very dangerous. It is not necessary to use pressure when casting resin, but it is very helpful because almost all bubbles can be eliminated in the casting.

Most clays will release from silicone just fine. Make sure that it is a sulfur-free clay or it will inhibit the cure of the silicone rubber.

Robert Tolone Thank you! Are you open to doing consulting work? My partner and I have a project we’re hoping to start in the near future and we would love to talk it through with you/get your feedback.

@@ereshkigalinanna6646 Send pics to roberttolone@yahoo.com. I’ll be happy to take a look at your project.

Robert Tolone Thank you!

It’s a business like any other. If you know how to manage a business you can run a casting shop. If you don’t know how to run a business you won’t succeed. So the only useful tip I have is to learn small business management.

I talked about that in this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NmrAm6h8jzU.html

Not necessarily. What is almost always essential is to use a parting agent. Silicone rubber generally sticks very well to itself, so if you are casting silicone against silicone you must have a complete barrier coat between the mold and the cast. your rubber manufacturer can recommend a parting agent that works with their products.

Thank you! Cheers!

Yes, I am a sculptor and mold maker full time. I buy my materials from www.Silpak.com. I use a variety of their rubber and resin products but primarily I use their Econosil-25 silicone rubber. That is the least expensive silicone rubber they sell. The urethane resin I mostly use is Silcast II. Silpak is located in Southern California but they ship anywhere. I’m not affiliated with them in any way; just been a customer for more than 20 years. Thanks for watching my videos!

@@RobertTolone that's awesome! I really want to do mold making full time but dont really know how to make that leap, right now it's just a side hustle and passion. Thanks for your reply Robert!

I often paint my resin sculptures. Most of the time I use artist’s acrylic paints. Sometimes I cast pieces of a sculpture in different color resins by adding dye or pigment to the resin. Both methods work fine but you should be aware that urethane resin castings color over time. It typically becomes darker and more yellow. So you will notice a color change unless you paint the sculpture.

My shop is primarily a prototype shop. So mold life is rarely an issue. But if I am doing a production run I estimate the number of mold cavities for the number of parts I need to make. I start with a 1 to 10 ratio as a rule of thumb. Molds of models with a lot of surface detail wear out faster than models with less detail.

Hi Albert, yes the brown wax I’m using to build the sprue is the same wax the sculpture is made of.

@@RobertTolone thanks Robert!

Yes, you can make bubble-free castings without pressure pots. Two things help: the most important thing to do is put vents in the mold so that the air can escape as the resin fills the mold. This video explains vents in detail: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-6Uqdmje3ZGI.html And be sure to use fresh resin and store leftover resin in airtight containers. Urethane resin absorbs moisture from the air very quickly and then it foams when you cast it. I buy resin 10 gallons at a time so it takes me a while to use it up. Having the pressure pots means I can stop the older resin from foaming. It can’t foam under pressure. Good luck with your casting projects!

Sure, I would wax the plaster. Be sure it’s completely dry.

@@RobertTolone thank you.

It was an original sculpture. For much of my career I have been a toy prototype sculptor for the entertainment industry. Kid’s Meal toys for fast food restaurants- that sort of thing. The sculpts are always done in wax which we used to be able to buy but now make ourselves.

Robert Tolone it seems these days 3D printing is the way of prototypes, but I’m fascinated by the hand sculpting process. With roots in illustration, I’ve recently delved into sculpture with Super Sculpey firm (checkout andersensculpting.wordpress.com) and I’m beginning to dream of sculpting and casting my own 3.75” action figures (a la 1970s Star Wars style)... yet I find that working in clay feels unfinished and the few instances I found online point to an initial cast in wax for refining the details that couldn’t be captured in clay. I’ve certainly picked up some wax tips from your videos, but I would love to learn more about your toy sculpting experiences and process.

Some clays like hard Chavant and Monster Clay will hold a tremendous amount of detail. But for a toy prototyping I have always preferred wax. It is the most useful and flexible material because it can be worked in so many different ways. Most of the professional toy sculptors I know make their own. The formula is a usually a combination of paraffin, carnauba wax, beeswax, stearic acid and other ingredients like talc and pigments. You can adjust the proportions depending on if you like your wax very hard or softer and stickier, etc. Truthfully it’s a pain to make because you need to grind in the powders. To sculpt it all you need to get going is a wax pen and some basic carving tools. But you can go full-on machine shop to work with it too.

Yes, they are pressure pots.

I never apply a vacuum or pressure to a model while pouring the mold. That is because the model may be hollow or have voids inside it that could get crushed or blow up. Clients bring me objects to mold and I just can't tell how they are made. I learned this the hard way. 😢 Also, if you pour the silicone properly it's not necessary.

That exact project is in the pipeline, coming up soon. The short answer is you have to have the jaw separate from the skull so that you can cast the teeth.

@@RobertTolone I will be watching that video. Thank you for your help.

Car bodies are extremely difficult to resin cast because they are thin walled and have very complex parting lines. I am going to attempt to cast one in an upcoming viewer project soon.

Manufacturers use a variety of techniques. There is injection molding, blow molding and rotational molding. In some processes the resins are granules and are poured into a heated metal mold where they melt and fuse to the walls. Other techniques pour molten resin into a mold and it cools at the walls first. They wait until the walls build the correct thickness then the remaining hot resin is then poured out. And of course many products are molded in sections or halves and the parts are fused together afterwards.

If you vent the mold cavity properly you should be able to make bubble free castings. The main reason I use a pressure pot is that I buy resin in 5 gallon buckets and it takes me a long time to use them up. Over that period of time the resin absorbs moisture from the atmosphere and this causes it to foam while curing. The pressure pot prevent this from happening.

@@RobertTolone ooohhh i see, i never knew that before you told me. Thanks a bunch!

@@RobertTolone also a curiousity, what does the resin model look like without placing in the pressure pot? Like does the recasted model structure would be compromised due to the foam or would it just be like the same thing from a fresh bottle of resin?

@@jedriclim It’s full of holes like a sponge and there may be voids where the resin foamed and didn’t fill areas of the mold.

cocain?

Yes, I have made molds many times from polymer clay sculptures. There are a couple on this channel: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lLtUFN0KAEg.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-apyI1q511iw.html Thanks for watching!

I think this is the tool you are referring to: www.foredom.net/product/k-wc-3-wax-carver-kit-7-tips-universal-voltage/

Biggest problem casting foam is that the mold must be strong enough to resist the pressure of the foam expansion. So my favorite rubber band method doesn’t work. Usually you would use a two-part silicone mold held tight in a strong mold case with lots of clamping pressure. Foam is very aggressive and it is best to use a mold release or barrier coat on the mold. Also, it is critical to get the amount of foam right so you don’t have extra foam trying to force its way out of the sprue and vents. A lot of people use self-skinning foam so that you get a nice shell around the foam interior. If you have not done so already, do some research on R.I.M. - reaction injection molding. That’s basically what we’re talking about here.

@@RobertTolone Thank you for the great info.

You could do it that way. There are lots of ways to make molds!

It is very helpful but not essential. Urethane resin attracts moisture from the air and that causes it to foam. I buy my resin in 5 gallon buckets and it takes me quite a while to use it up. Over time the resin absorbs moisture no matter how carefully I seal the buckets. The pressure pots prevent the resin from foaming while the castings cure in the mold. If you use fresh resin you can make castings without pressure pots provided that you have designed the vent system correctly for your model.

@@RobertTolone : I wonder if you could add a floating styrofoam disk or membrane to the inside of your buckets if it would keep the most air separate from the liquid resin. Or for that matter, a silica gel package to soak up the moisture. Especially if the top of the bucket is not very open to the air. Just a thought.

@@garywheeler7039 What most people do is attach a moisture trap to the bucket. It’s just a tube filled with a substance that absorbs moisture from the air. The chunks are pink and turn blue when they have absorbed all the moisture they can. or maybe they’re blue and turn pink, honestly I can’t remember. you can bake them in the oven to drive off the moisture and reuse them over and over. We used to attach them to 55 gallon drums of resin when we were doing big projects. Another way to go is to fill the bucket with an inert gas that is heavier than the atmosphere and lays on the surface of the resin preventing moisture. Personally I found all of these solutions cumbersome. The best way to deal with atmospheric moisture is to use up the resin as quickly as you can and cast everything in a pressure pot. The pressure pot solution is much less expensive than all of the solutions surrounding atmospheric moisture prevention.

@@RobertTolone : Yeah, I have used desiccants with similar properties. Sounds like you are on top of things!

It would depend on the shape but I don't see why not.

Email me at roberttolone@yahoo.com.