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Post by notoes on Jun 20, 2018 13:28:33 GMT -5
Got a "double check my math" question on the ratio for shrinking a mold question. I've seen (and saved the info) on how to make a mold shrink by adding Odorless Mineral Spirits at like 1/3 the total weight (or is it volume?) of liquid mold material and after de-molding, the Mineral Spirits evaporate after seven days and the mold shrinks by somewhere around 1/3 of its original size.
What I'm trying to do is this: I am making my own personal set of clay alphabet stamps in resin in at least two fonts - a cursive type and Times New Roman font. And I need them no bigger than 1/4" tall. And I'm making them myself because none of the stamps (for clay or ink) I've found have deep enough pockets to make nice deep letters. I need them deeper than you'd find normally because I'm imprinting on clay which I then make a mold of to cast resin in so I have a resin casting to make the food safe molds from (instead of a clay one) and for the lettering to show up very well on the candy/chocolate made in those molds it has to be a bit deeper than normal. And not only are all stamps (for clay, ink, AND metal) are fairly expensive and most times they are also larger than I want. Plus I want at least two different fonts and that just adds to the problem.
So my math on doing this is: Using 3oz (total) of liquid mold rubber, I add 1/3 oz of Odorless Mineral Spirits, mix well and pour into mold box with castings glued to bottom. Then after de-molding the castings, I wait 7 days and the mold should have shrink about 1/3 less than the original size.
I'm figuring that if I have castings that are about 1" tall, once shrunk the cavities should give me somewhere around 3/4" tall castings. Hopefully. Can anyone verify my math will work out anywhere close to what I hope for? |
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Post by Brian on Jun 23, 2018 12:28:46 GMT -5
...Never heard of shrinking a mold before...doesn't mean that it cant be done. I do recall in one of my many conversations with large scale modeler Bob Hayes of soaking the mold in something to increase its size. I've e-mailed Bob with your question...if there is anyone in the world that would have the answer , it would be Bob. Will let you know when I know........ |
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Post by notoes on Jun 23, 2018 18:41:07 GMT -5
There's a video on doing it on the bait making section of Alumilite's site using HS-2 for a fish bait mold. Thanks for the help.
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Post by Brian on Jun 27, 2018 22:29:17 GMT -5
There's a video on doing it on the bait making section of Alumilite's site using HS-2 for a fish bait mold. Thanks for the help. Guess I need to visit that section more often...my apologies for the delay in response...... The mold shrunk by 30% aprox. in the video....assuming that you have added the correct amount of mineral spirits to the mix by determining the WEIGHT of silicone and catalyst combined ... I take it that your original/master/buck is 1" tall 30% of 1" = 0.3" (1.000 - 0.3 = 0.7) 0.7 of 1" is 13/16th of an inch. or 17.78mm.
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Post by notoes on Jun 28, 2018 7:35:33 GMT -5
I found it while I was looking up something else myself.
Yes it is about 1" tall. So my math on that seems to be right then, thanks.
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Post by paraviper on Jul 1, 2018 0:09:39 GMT -5
Carroll advised me against it on the phone once Notoes. Reason is that you may get a distorted shrink of the mold with uneven proportions. The only two products I would recommend are either reduce it 2.0 or Hydro-span. I've never used the Hydro-span product. However I've used the reduce it 2.0 and had some success. Look up a company called pink house studios on the web. The process works by making a regular mold of the item you wish to shrink. You then poor your reduce it into the mold just like you would any other resin. I would advise coating the mold with a bit of Vaseline to help with the release of the reduce it. The material itself has a rubbery type of consistency so if you don't add a release of some kind it can tend to stick. The material is mixed in a 2:1 ratio..two parts water one part reduce it. Make sure you get some bloxogen to spray in your can of unused reduce it as it has a short life span otherwise due to air contamination.
Your part will take 7 to 10 days to fully shrink.You can expect a shrink rate of 40 to 60 percent each time you do it. If you need to stop the process at any point.... because maybe your part has reached the correct size but you know it's going to keep shrinking.. Make a mold of the item at that point using platinum silicone as this will stop the shrinking process. Don't use tin cure as it will keep shrinking and you'll have to start all over. Hope this helps.
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Post by paraviper on Jul 1, 2018 0:34:33 GMT -5
Oh I forgot to mention it works by evaporation and at first the material will be a bright white color. As it cures and shrinks it will turn a yellowish clear kind of color. Maybe I can post some pictures of action figure heads Ive shrunk to give you an idea. I'm not savvy on how to upload pictures on this forum though.
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Post by notoes on Jul 4, 2018 5:35:43 GMT -5
Distorted is okay, I can fix that. To post pictures in a reply you have to go click on the Reply lettering on the right instead of the Post Quick Reply button under the Reply box you type in. It should give you the full formatting box with the Add Attachment option. Took me a bit to figure it out myself.
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