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Post by catspraise on Sept 12, 2018 12:14:25 GMT -5
I need to reverse engineer a mold from an existing plastic mold I have. If at all possible, what can I do to ensure water clear will pop out clean from the original plastic mold? The original mold was made for casting concrete stepping stones. All suggestions & ideas are welcome.
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Post by notoes on Sept 15, 2018 20:09:52 GMT -5
Could you attach a picture? There's at least two ways you could do it but I'd have a better idea of which would work better for you if I know what it looks like. Personally, I prefer to not use my plastic chocolate molds when I can and I have actually made molds of the plastic ones so that I have silicone ones that will last a lot longer.
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Post by catspraise on Sept 19, 2018 11:15:36 GMT -5
Could you attach a picture? There's at least two ways you could do it but I'd have a better idea of which would work better for you if I know what it looks like. Personally, I prefer to not use my plastic chocolate molds when I can and I have actually made molds of the plastic ones so that I have silicone ones that will last a lot longer. Like I said, it's just a plastic mold for making concrete stepping stones. I cannot pour over the outside because the finish is not smooth or shiny and the design is not as clearly defined as needed.
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Post by notoes on Sept 20, 2018 6:03:13 GMT -5
Actually I'd go with making a new mold out of silicone - even though it's a lot of extra work. It's just my personal preference to not use plastic molds when I can.
Method #1 What I would do is pour one of the stiffer rubbers (HS-1 or one of the Flex series might work) into the plastic original as if it was concrete and when it cured, make a mold of that to use. My reason for that is plastic is limited on what you can pour in it (even heavy duty plastic) and silicone will give you the "stretch" you might need when de-molding the concrete. You'd end up not using the plastic mold after the first cast, have a silicone stepping stone, and a silicone mold to replace the plastic one. It's a few extra steps to create a silicone mold copy of a plastic one but the silicone one would last longer. Though make sure you clean the plastic up very well before you cast the silicone in it.
You also said the design isn't a defined as you would like. As to that, once you get the silicone copy mold done you could cast regular resin in it and sand down the regular resin casting until it is just the way you want it and then cast a second silicone mold of the perfected design. You would end up with two molds (one nice and smooth and the other suitable for casting concrete) but that might be the way to not chance cracking the plastic mold.
Method #2 Or you could use an air dry clay and cast it in the plastic mold then once it's dry you could sand it smooth and make a silicone mold of the better surface. That way you would end up with just the one mold and a clay casting but there would be the added risk of cracking the plastic mold. Then again, if the plastic is in good enough shape and heavy duty enough, it might just work okay.
Hope these ideas help.
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Post by catspraise on Sept 24, 2018 7:51:43 GMT -5
Thanks notoes! Great ideas.
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