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

Dereck Turner

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

  1. Shahid Ansari says:

    Wao lovely video

  2. TurboFlush says:

    Why is it you always find the video you needed the week after. Lol.

  3. TurboFlush says:

    So when scraping the clay.. is it level with outside of model? Leaving the thickness of model into the clay?

  4. ziad alhouri says:

    Thanks so much….. Amazing

  5. Purwo Erdiantoro says:

    Thanks…..for the CLEARED tutorial……

  6. Aquarium Channel says:

    +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?

  7. Rodder Files says:

    How many clean bodys can you get from that mold ?

  8. phreaktor says:

    Can task 4 be painted or Plastidipped?

  9. shonta ford says:

    Can you cast silicone in a silicone squish mold?

  10. Reece McCormack says:

    That was interesting, but where would I get a vacuum chamber from?

  11. Al W says:

    Hello Milo, Where do you get your projects from?

  12. David Gomez says:

    Please 3d print a zenki 240sx than sell it I will buy haha

  13. ThomasConservative says:

    I'm inspired… I will buy it all !

  14. Crushing Vanessa3 says:

    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.

  15. Zipo214 says:

    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.

  16. pprotory says:

    Would like to see a video like this but using vent sprues and either injection or pour method.

  17. Sajan Sebastian says:

    Do you have video on rail track casting?

  18. Doc Reasonable says:

    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?

  19. Vitaliy Oleksishen says:

    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?

  20. Steve Bowen says:

    I notice you used pressure to avoid gas issues rather than vacuum. What is the reasoning behind that?

  21. Rock Fish says:

    It looks like you have funn doing it.

  22. Rock Fish says:

    How about a humen hand?

  23. ndara ndara says:

    nice and easy learning thanks.

  24. MuffinMan0521 says:

    I really like the nice looking graphical product pages on their website. Makes it really easy to understand which product is right for the job.

  25. ari Tench says:

    Excellent video thank you so much!

  26. J K says:

    I have a question: how do you know how much resin to use? Is there a calculation you use like volume displaced by the car body? Or do you guesstimate?

  27. RENNAgade Cosplay says:

    Can you pressure cast a squish mold?

  28. fiskusmati says:

    How you dealing with thin screw holes seen in 6:58? You block them, and then later drill out in every casting?

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