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Mold Making Tutorial: How to Make a Silicone Squish Mold for Casting a Plastic Model Car Body

Mold Making Tutorial: How to Make a Silicone Squish Mold for Casting a Plastic Model Car Body

Molding and casting a diecast car body using SORTA-Clear 37 and TASK 4 My main objective for this project today is to make a detailed mold of the original model so that we can reproduce many detail castings in a variety of different finishes, and for this project I’m going to be using the SORTA-Clear 37 which is a translucent silicone molding rubber. Now, for the casting of our project I’m going to be using the TASK 4 which is a performance urethane resin, and it’s very strong in thin sections so it’s going to lend itself very well for our project here. My model for this project is a diecast car body that I’ve prepped by removing all the loose parts from, and only the shell remains to be made a mold of. To start I’m going to build up about an inch high clay bed out of Sculptex oil-based clay that is sulfur free. Now, keep in mind whenever you work with a platinum silicone you want to make sure that you use a sulfur free clay so that you don’t inhibit your silicone product. Now, all the edges of our clay bed are beveled inward towards the model and what this does is going to create an essential part of the mold because it will act as a key, a large key, all along the perimeter of our model, and this will aid with the alignment of the two halves of the mold. So what the clay does here it actually acts as a barrier for the first half of the silicone mold that we’re going to pour. Everything that is clay at this point will then later become the second half of our two-part mold Now, this is going to be the most important and most time-consuming part of the mold making process so take your time and make sure that those lines between the original model and the clay-up are as clean and as precise as possible. This is going to limit our amount of time spent on cleaning any of the castings that come out of this mold So now that our model has been fully clayed up, it’s time to take a sculpting tool and bring back some of that clay so that we have a clean and precise line between the clay-up and our model The attention to detail in this step is going to allow us to reproduce better and more precise castings. To add some keys to our mold, I’m simply going to use the acorn nut that I’ve screwed onto the back of this bolt which makes it an easy to use key tool. Now, note that I’m pressing the windshield keys straight down and not at an angle so that they don’t become an interlocking mechanism between the two halves of our mold So now that the model is fully prepped the keys have been applied and we’re ready for the next step, and that’s the assembly of a mold box. Now, I’m using some Plexiglas for this application here purely for the visual purposes but you can use almost anything to contain the silicone in making a mold box Make sure that all the edges are thoroughly covered with some hot-melt glue so that we don’t have a leak spring while we’re pouring the silicone. Now, the silicone that we have chosen for this project is the SORTA-Clear 37, and the reason for that is it has an easy to use one-to-one mix ratio by volume, and because it’s translucent I’ll be able to see into the mold as we’re casting. Now, keep in mind that these products do separate in storage and transportation so it is very important that you premix your parts A and B before dispensing, and since we don’t need a gram scale I’m simply going to mark my dispensing cups one-to-one by volume and proceed to dispense the Part A and Part B. Now, something you have already noticed in the product is the lack of pigmentation. There’s no color in the A or the B so it is going to be very important that we get a thorough and a good mixture of the components by scraping the sides and the bottom of your mixing container. To ensure a proper mix between the two components, I am going to go a step further and pour the mixed silicone into a second clean mixing container and repeat the mixing procedure. So, the mixing process of the product actually introduces a lot of air to our silicone, and to get rid of any of the bubbles that are trapped in the silicone we’re going to proceed to vacuum de-gas the product. Now we’re going to subject the silicone to 29 inches of mercury until the product rises and falls, and we’re going to keep it under vacuum for another minute and let it just kind of bubble and pull any kind of air that’s trapped in there The silicone has been vacuumed de-gassed and can be now poured over our model, and to do so we’re going to pour it in a thin stream from up high and let it hit the lowest point of our mold and let the silicone slowly make its way up and level itself out Now we’re going to allow the silicone to cure for about four hours before de-molding. It’s now been four hours and we are ready to de-mold our first half of the mold. The mold is clear and translucent and we’re able to see the actual car model inside. Now we can simply remove the board and any of the clay that was inside a model. You want to take extra precaution when removing the clay so that we don’t disturb the silicone and the model inside. As you can see here I used a wooden tool so that I wouldn’t put any scratches onto the model itself, either. Once our mold has been thoroughly cleaned and all the clay has been removed, we’re ready to apply some release agent to make sure that our two halves come apart once the mold is fully cured, and for this application I’m going to be using the Ease Release 205 and the reason why I’m using the 205 is because it is a liquid component and not a spray. This is going to ensure us a thorough coverage of release agent on the silicone, and as an extra precaution I’m going to also put some release agent on the outer edges of the mold and let this now dry for about 15 to 20 minutes before proceeding to the next step Now that we’re ready to reassemble our mold box, we want to make sure that those mold walls are nice and tight against the silicone so that there is no space for the freshly poured material to seep down and underneath Now we’re going to follow the same mixing procedures that we did on the first half of our mold by double mixing and vacuum de-gassing of the silicone We’re ready to pour the second half of our mold, and just like we did on the first half we’re going to pour from up high and let the material hit in the lowest point and seek its way up on its own The silicone is now allowed a full cure for four hours before de-molding And now the moment of truth, we’re ready to remove the mold walls and peel the two halves apart. As you can see, the two halves come apart quite nicely and we can simply pop the original model out of our mold by flexing and squeezing it out To give our casting a nice metal-like finish, I decided to use some Cast Magic Bronzonker, which I’m going to brush on using a chip brush to both sides of our mold. By applying some Cast Magic Bronzonker to the second half of our mold, we’re going to reduce some of the clean up that we have to do afterwards since the seam line is going to have the same finish as the rest of the car body, and for the casting resin we’ve chosen to use the TASK 4 performance urethane casting resin because it is very strong in ultra-thin sections and lends itself very well for making models like these. Now, just like we did with the silicone we want to make sure that we thoroughly premix the Part A and Part B before dispensing. Because this is a one-to-one mix ratio by weight, I’m going to use an accurate gram scale to dispense the Part B and I’m going to pre-tint it using some UVO Brown that will play off the Cast Magic Bronzonker that we dusted the mold with. Now, because this is a urethane-based resin I waited to dispense the Part A so that I don’t expose it to the atmospheric moisture When mixing the resin together always make sure to scrape the sides and the bottom to ensure a thorough mixture of the two components. We don’t want to have any unmixed material clinging onto the bottom of our mixing container. So now that our resin has been mixed we can simply pour it into the bottom half of our mold and then proceed by squeezing the top half down into that, and because the mold is translucent we can actually make sure that the resin fills the entire mold and we get a precise casting Now, something else I like to do to kind of keep the casting as precise as possible is add some weight to the top of our mold, and what this does it actually holds the top half down and prevents it from floating around and casting a thick car body that wouldn’t be as precise, so we’re just going to allow this to fully cure now for 16 hours before de-molding So now that our resin has been fully set up I am simply going to peel away the top half of our mold, and I’m gently going to squeeze the mold to release the model, and there it is as simple as that Here we can clearly see the benefits of taking the time to build up that clay nice and clean because any of the flashing between the doors and the windshield is hairline thin and can be easily peeled away just by using your hand. The TASK 4 is very strong when cast in ultra-thin sections and this model here is only about two millimeters thick, so while very thin it still retains its shape, and after much flexing and bending it is very strong and will not break. And here you have our original model next to our casting that looks 100% identical Now, if you got inspired and would like to purchase any of the products that we used in this video today, you can do so by visiting any one of our distributors around the world. So there you have it a simple and easy way to make two-part squeeze molds using the SORTA-Clear 37 platinum-based silicones. Now, if you have an idea about what we should mold next, let me know in the comments below And if you want to see more videos like this, please hit the thumbs up button And to keep up with our latest mold making and casting videos, remember to subscribe


This is an interesting video – thanks. I have an idea for a project which I suspect this would be very useful for but the object to be cast would be an automotive light front. The current item is glass and the casting material would need to be UV-resistant and impact resistant as well as strong enough not to crack readily.

I'm in the UK – would it be possible to discuss this requirement with someone from your technical department?

Thanks again.

Great video.
I plan on casting a single-gang drawn electrical handy box using a crystal resin. Would the process be the same? I'm worried about breaking the "screw tabs" (that point toward the inside of the box) when separating the two silicone halves.

Thank you for an excellent tutorial video. Nice easy teaching style and crystal clear to understand. Do you have a distributor in U.K.?

I'd like to see a video about "reproducing" an IMperfect plastic part – i.e., how to make it perfect first.

just a Idea I'm trying to make a copy of a aluminum mod and was wondering if this product will work for me

i was making a reproduction of the porsche 911 turbo targa body for a rc car restoration
thin edged front windshield of a cabriolet car, is what i would like to see made 😛

I'd like to see a tutorial of how you would mold something that would have internal voids, like a intake manifold.

yes im really inspired. I got an idea what about lego bricks or lego minifigures . good lord lego are not cheap.

After making this part would all the other missing bits need to be cast from the same material? In other words could I just glue other parts made of different materials to this, like styrene?

Thank you, Thank you, Thank you. I have always been interested in resin casting and after watching your video I am excited about the process of making car bodies and parts. I am going to watch the rest of your videos. Also, I have never used resin before so I really appreciate you sharing the process of using it as this is how I learn more about it. Thanks. Jeff

Great ,that's amazing like magic and better then 3d printers . I need to mold a bullnose propeller for my quadcopter would you show how to do that ?? thank you .

I think that's the first time I see this kind of video without going mad at mistakes.
It has been great to seen for once someone knowing what he's doing!

Great tutorial.
Thank you!
Anywhere I can find a good info resource site about the various molding plastic types, and their properties, for the type of cast I want to achieve?

Excellent teaching, clear, precise with no time wasting waffle..Thanks. Just one question; do you use any solvent/s to clean any part of the master or mould?

i was just amazed on what your product can do, can i request for you guys casting a 1/24 tires and rims too?

Wonderful tutorial; thank you so much! I'm completely new to mold making and casting, and found this very helpful. Wish me luck!!

I always look forward to the Milo versions of the Smooth On videos. His calm and instructive voice keeps my attention.

How does TASK 4 compare to ABS according to stiffness. Would it be possible to cast DIY enclosure for electrocnics with it?

I'm Nipon from Thailand
I would like to make a business and would to be use your product for the creation the wheel eyebrow (like ford ranger), Can you do to show me how to making ?
Thank you

a video of molding things like air filter covers or plastic parts for lawn equipment parts like that would be great. due to some being obsolete .thanks

Hi. I am new with this. I want to make molds mostly to use with edible things like fondant, gum paste and chocolate. which Sorta clear version is better for my projects? 18 or 37? I haven’t seen a video using sorta clear 18, so I don’t how hard it is once is cured.

There is a huge demand for 1/9 scale remote control truck bodies. The prices people are willing to pay for similar product ranges from $30 to $90. Look into it. There is money to be made!!!

Can i ask something?

I want make flexible cast
( figure's hair or cloth…)

Can i ask that material's name?

My english is not skillful so i can't understand your move perfect..

Please give me tip

I really loved it but its good for fun and hobby as the cost of material does not justify the effort. Or you make something you can sell onwards, copies.

جميل جدا رغم أنى لا أجيد الانجليزية ولكنك محترف شكرا لك

how do you determine the amount of resin needed the calculator on the site doesn't explain how to estimate like a car body it only has solid object measurements?

Hey I wan to do a casting or a scale car model like the one that you used on this video. But i have never ever done any molding or casting work. Can I use the same silicone that you used on this video without the vacuum spet? I dont have anything to do this step vacum out the air bubbles.

The casting is for a proyect of a small car robot. And i expect a lot of tear and breaks if the casting is rigit plastic, on the process of testing the robot. So It would becaome handdy to have a few scale car models that are a little flexible and strong like the casting you did on the video.

Your videos are really helpful! I'm wondering if there is another way to prevent bubbles while mixing sorta-clear. I don't have pressure equipment, as I am making molds of very small things. I've heard putting them in the fridge for up to six hours works really well, but i was wondering if you guys had any thoughts. Thank you!

I would like to make a mold of my Commodore Amiga 500 case and cast it in transparent green resin. Can you recommend a resin and also since the case is just like this model only larger, is there a special silicone I should use so the mold does not sag under its own weight and possibly make the casting uneven? Thank you.

for those that don't have an pressurize, just tap your silicone, like plaster. the bubbles will still reach the top.

And you are video to be very inspiring and very helpful I probably liked and prescribed you as well can you show us how to do a 1972 Blazer mold thank you

If making a mold for tail light. How do the color get added without amber running over to the red, and blending together?

Hmmmmmmm…. I think its time to do this for lego 12V train motors and wheels… Lego refuses to remake them, so….

+Smooth-On have a 7.5 g glass aquarium with an acrylic lid. Dimensions are unique design. It's backside is 15.72" L X 10.75". It's backside is a straight edge but the front side have rounded corners. I want to upgrade the cheap lid it came with to a thicker (about 5mm) clear resin or epoxy lid… if it didn't have the rounded corners on the front, I could simply have Home Depot cut a rectangular top but this requires something curved at the corners. Your thoughts?

Does Task 4 take paint well? It takes 16 hours to set before demolding? What's the shelf life once opened?I just want to know because I used the quick setting one and there's usually not enough time once it's mixed to get it in the mold and one part of the resin and OOMOO always dies on me so it has to be thrown out. Also no one mentions pressurizing of the resin to get it nice. Good products, just a few rants.

If I wanted to make a mold of a very delicate game board figurine, would this be a good choice?

Obviously on a smaller scale but my biggest concern is the mold breaking the original figurine. It’s one of a kind.

Excellent. I'm wanting to cast some very small delicate pieces, and I'm thinking I should use Mold Star 15 silicone with Task 4 resin. Just wondering if you'd agree that's a good choice?

Great job!

Thank you!
I can not choose a similar plastic, but with high heat resistance. Maybe it's TASK 8.

Does it have similar mechanical properties for thin section castings?

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