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Scale Car Garage - Mold making & Casting Pt. 2

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  • Scale Car Garage - Mold making & Casting Pt. 2

    Please join me for part two of an illustration of how to make molds and cast parts at Scale Car Garage!

    Any and all comments are more than welcomed!


  • #2
    Thanks for the video. I don't know how many people will have the triple beam scale. A digital scale might make things easier by placing the empty mix container on the scale and using the TARE button. this zeros the number. then add the material to the weight required.

    Question: your rtv silicon seems to have long working time. The stuff i have, has a short pot life, requires me to work quicker than i like. sometimes i am little short on silicon after mixing and pouring causing a thin wall or roof. how do you know how much you will need to mix?
    I trying to make a 2part silicon mold of a Datsun and using a slot it clear case as the mold box

    i'm using Smooth-on Mold star 30, 1:1 by volume, potlife- 45min, cure time- 6hr. When i spoke to representative, they said it does not need to be vac degassed. I'm not using a vac chamber, getting stuff together for this, but may not have enough time with the limited pot life of this product.
    Last edited by lance; March 16, 2021, 02:40 PM.
    Lance Sofa racer


    • #3
      Nice one. Everyone has their own methods.

      Here is the standard I go by written by who I consider to be one of the masters of this art.

      Making A Resin Body Master by Mark Thomas


      • #4
        Originally posted by HomeRacingWorld View Post
        Nice one. Everyone has their own methods.

        Here is the standard I go by written by who I consider to be one of the masters of this art.

        Making A Resin Body Master by Mark Thomas
        Love that mans work and I actually have that body waiting for some love !


        • #5
          Lance, mold Max 30 has a pot life of forty-five minutes and a cure time of twenty-four hours, it is a tin cured silicone and the standard for industrial and art related applications including making molds for reproducing prototypes, furniture, sculpture and architectural elements.

          Mold Star 30 is platinum silicone with the same pot life and faster cure time of six hours.

          Mold Max 30 (at least here in Canada) is half the price of Mold Star 30.

          As far as how much silicone to mix, it is based on the relationship between mass and volume, determined by the increase in the density of the silicone after de-gassing. To be honest, I've never been able to very accurately determine the relationship.

          So, I always have an "in process" mold waiting for any 'extra' silicone (you can spot a partially filled clear container on the workbench to my right) to accept the surplus.

          If you do fall short on a pour, fear not, just add more silicone to your mold, even if it has cured! Silicone only bonds to silicone!

          I hope this helps!

          Harry, thanks so much for the link!

          Looks like we have the same methods with some minor variances!

          Wonderful work!

          Thanks so much for watching, posting and subscribing!


          • #6
            Once you have your master and mold box done up, you can pour in rice to fill the void. Empty the rice into a measuring jug and that will give you a good approximation of the volume of silicone you will need. Mix a little more to ensure you have enough. If I have left over silicone I pour into a round lid. Once cured it makes a great base to mix paint on. Not many paints stick to silicone. When the paint dries you can just peel it off leaving you a nice fresh paint mat again.




            • #7
              Dan, great tips!

              Thanks so much!


              • #8
                Just wanted to thank you for taking me down memory lane with that triple beam balance. I think I last used one of those in high school chemistry. Since then it has all been digital analytical balances and top loaders. And the white lab/shop coat makes it even better. But hold on a second, are you working in your shop with bare feet? Kind of looks that way. Enjoying the videos, keep 'em coming.



                • #9
                  Peter, my pleasure!

                  I'm so pleased that it brought back some memories for you! (No school like the old school!)

                  The white coat is the one I wore when I worked for Gulf as an undergrad in the lab!

                  Yes, busted, I'm a barefoot guy!

                  Thanks again so much for your most valued support!


                  • #10
                    Another great video John. Good in depth, all details clear.

                    I use a cheap Harbor Freight jewellers scale. They are under $10 and you can put your mixing container on the scale and punch the tare button to re-zero. These scales have several modes. Grams seem to be best for small mixes. It is pretty easy to do a 10 to 1 mix or a 1 to 1 mix with these little digital scales. I also have a largr postal digital scale that operates the same way, but has a much bigger bed if you need a big container like you use to de-gas.

                    With the simple air cured molds I do, it's pretty easy to keep a stock of small Dixie cups on hand and bigger throw away plastic cups.

                    I like to use a glue gun and corrugated cardboard or the corrugated plastic yard signs from the last election to make a mold box that is big enough, but not too big for the master. I don't like to use more rubber than necessary, although it is easy to trim old molds or a mold too big and chunk up the rubber for filler in any new molds you pour.

                    I use the High Strength from Alumilite and it is really soft. If the mold sides are weak, I find a couple pieces of thin plywood on the outside of the mold box, held by rubber bands to keep the mold the right shape and not let the sides bow out a little. If you can re-use the mold box, you can just use it to keep the mold the correct shape.

                    I always have something in a mold box in case I have extra silicone mixed up. Usually just a driver figure or driver head, maybe a body mount.

                    Some guys use pressure cooker or paint pressure tanks for vac or pressure tanks.

                    Matt B
                    So. In