Could you please let us know which of them do you use for Molding jewelry parts ?
Thanks
Recommended Casting Set Up
Re: Recommended Casting Set Up
it depends on what you're looking to mold.
all polytek are grouped by their material type and shore hardness.
for instance, i started out using platsil 71-35, 71 being the platinum silicone material with a shore hardness of 35. there is 71-20, 71-30, etc.
problem with the lower shore hardness, if you are doing pieces with very fine details, you'll need higher injection pressures and lower temps. this may sound counter-intuitive to have LOWER wax temps in order to gain fine details, but the hotter your wax the more shrinkage (it will shrink back from details). i'd use 10-15 psi, and 145*F (min temp was supposed to be 155*F). i found that i had much less shrinkage. also, i'd put my molds in the freezer for a minute to make sure wax hardened quickly.
now, with that, the higher pressure means that you're going to lose dimensional accuracy. so then i went to polytek 75-70. 75 series is polyurethane 1:1 material. shore hardness 70. shore hardness 70 is very hard compared to 35, so it retains better dimensional accuracy under pressure, and with proper mold making technique (you MUST degas) you shouldn't have a problem. thats a 24hr cure material, but i would bake it at 150*F in the toaster oven, and it would be good ~8hrs after pour (i'd pour the material, and bake the next morning for ~1hr)
these are materials i've had success with. i use the 71-35 for molds that i don't need accuracy. i have a mold for my sprue tree, for instance. now that the B9 Yellow is a major improvement over the cherry, i don't need to make molds of jewelry. (can't wait for the reify castable, btw)
call polytek and speak to Tom, he has helped me a lot in making a decision. polytek has very good customer service. he suggested the 75-70 to me, and i was very pleased, 1:1 ratio (71-35 is 10:1) that stuff isn't cheap, and you need to have some sort of gas to store the material. they sell argon in a can so that you can displace air/moisture from the jar after you are done. moisture will harden material.
don't forget you'll need a form to pour your rubber into. the smallest possible form to limit wasted material the better.
all polytek are grouped by their material type and shore hardness.
for instance, i started out using platsil 71-35, 71 being the platinum silicone material with a shore hardness of 35. there is 71-20, 71-30, etc.
problem with the lower shore hardness, if you are doing pieces with very fine details, you'll need higher injection pressures and lower temps. this may sound counter-intuitive to have LOWER wax temps in order to gain fine details, but the hotter your wax the more shrinkage (it will shrink back from details). i'd use 10-15 psi, and 145*F (min temp was supposed to be 155*F). i found that i had much less shrinkage. also, i'd put my molds in the freezer for a minute to make sure wax hardened quickly.
now, with that, the higher pressure means that you're going to lose dimensional accuracy. so then i went to polytek 75-70. 75 series is polyurethane 1:1 material. shore hardness 70. shore hardness 70 is very hard compared to 35, so it retains better dimensional accuracy under pressure, and with proper mold making technique (you MUST degas) you shouldn't have a problem. thats a 24hr cure material, but i would bake it at 150*F in the toaster oven, and it would be good ~8hrs after pour (i'd pour the material, and bake the next morning for ~1hr)
these are materials i've had success with. i use the 71-35 for molds that i don't need accuracy. i have a mold for my sprue tree, for instance. now that the B9 Yellow is a major improvement over the cherry, i don't need to make molds of jewelry. (can't wait for the reify castable, btw)
call polytek and speak to Tom, he has helped me a lot in making a decision. polytek has very good customer service. he suggested the 75-70 to me, and i was very pleased, 1:1 ratio (71-35 is 10:1) that stuff isn't cheap, and you need to have some sort of gas to store the material. they sell argon in a can so that you can displace air/moisture from the jar after you are done. moisture will harden material.
don't forget you'll need a form to pour your rubber into. the smallest possible form to limit wasted material the better.
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