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Stephen

Air Release Mold Dies

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Stephen    139

I could really use some input. We have an air release mold system that I am adding a few dies too. The instructions are pretty straight forward but I am having a hard time with a couple of decisions on sourcing two of the materials.

 

1) The rubber for the models.

 

We are making the models in clay and then making master molds from them to be able to cast a new set of masters in rubber so that we can use these new masters over the years to remake the working dies.

 

The instructions I have to do this just call for a rubber urethane. There are tons of choices but I can find none that are specifically for mold masters. I was thinking of using Sharkthane Flex Pro 70-20  (2qt A/B 1-1 mix $35) that In spite of its name, sets hard. There are dozens of options and price ranges. I was hoping someone might have input on a good rubber for this purpose. Most seem to be flexible which for the mold itself would be great but for a master model I thought it should set hard. Is this a reasonable assumption?

 

2) The plaster for the working air release dies.

 

The instructions call for Ceramical but when I went to buy it my local supplier assured me that Hydrocal was fine since he didn't have Ceramical. Since this happened last summer (I know, I know) I need to toss the Hydrocal I bought then and buy fresh so I was researching the issue to make sure. I did find this link:

 

http://shop.clay-planet.com/plaster-2.aspx

 

and they are clearly not the same but I was hoping someone could chime in if they have used such a substitution. My local supplier has a bag of Hydrocal for $25 but the only source I can find Ceramical is on the other coast and it is going to cost $60 to ship me a $30 bag of the stuff. i'll spend the hundred if I need to but obviously would like to have a local $25 source. 

 

 

 

 

 

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Mark C.    1,807

Those specs are very close except for the expansion % betwween hydrcal and Ceramical as well as a 1500# differeance oin compression strength.

I would just use the Hydrocal and be happy

 

Now as to the rubber masters -I have had a pro make mine a few times-the rubbers have been a bit different but are pretty hard for the masters.I would ask him about this except he has passed away.

The quaility rubbers are spendy-I have masters in a green runner and a brown rubber-both are very stiff.I cannot say what they are exactly. You may want to contact a master mold person on this info.

Mark

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Stephen    139

Thanks Mark, that's kind of where I was leaning. It is the expansion that gave me pause. Wouldn't put so much thought into if the process of making one of these air release dies was not so involved.

 

Here's a piece written by Jonathan Kaplan

 

http://ceramicartsdaily.org/wp-content/uploads/2010/06/knowyourplaster.pdf

 

on this site. Unfortunately he doesn't mention substitutions.

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Mark C.    1,807

He does mention Ceramical as the industry standard-That alone may enough to order some fresh stock up. I will add fresh plaster is what you want to use.

Mark

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Stephen    139

Thanks again Mark for the input, was greatly appreciated. A shout out to George Ullrich at Sheffield Pottery, he helped me source Ceramical on the west coast so I was able to go with it without having to pay three times the cost.

 

Shipping 1 or 2 50lb bags around the country can sure get expensive.

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JBaymore    1,432

You are hydraulic pressing, right? What is the press pressure you are using? That could give you a hint if the lower psi material is at all suitable. Most of industry is now dry pressing.... with very high pressures. If you are using a SM process, your press pressures are likely lower than the "industry standard" these days.

 

best,

 

..................john

 

PS:  Sheffield's "good folks".

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JBaymore    1,432

Shipping 1 or 2 50lb bags around the country can sure get expensive.

 

I sometimes ship "Grogzilla" from Clay Planet out there on "the other coast" to this coast... and yeah........ costs a fortune these days.

 

best,

 

...............john

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Stephen    139

Hi John,

 

No actually I am using a hand press with air purged molds. Works well for doing a session of sprigs or small tiles without having dozens of drying molds all over an already to crowded studio.

 

Not sure we will ever add an hydraulic press, just seems a little to automated and this just feels a little more basic, physical and connected to the process. I like that. Being an equipment junkie is hard to resist the bad boy though :-)  

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JBaymore    1,432

If you are hand pressing........ you likely don;t need the high strength plaster version.

 

I think you are the only person I know of that uses air-release molds for non-hydraulic work.  Interesting.

 

best,

 

...............john

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Wyndham    98

I have used  a hand press  for  a home made tile air release system. The hydrocal should be fine but if you wanted a little softer die then add about 25 % plaster to the hydrocal. Hobbylobby should have some silicone rubber for the masters.

If you need another source, give Rampress a call and find out what they recommend.

Wyndham

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Wyndham    98

This is the Texas tile press but I did mine for about $20 with a wood frame, air tubing and a compressor I had from HF.

Mine work fine for about 200 pressing before I made another mold.

Wyndham

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Stephen    139

My Ceramical mold is well past 200 pressings (maybe twice that) and so far is not showing any issues. Are yours losing detail or are the molds breaking down?

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Wyndham    98

Mine broke down early, but I was not as kind to it as I should have been. I used a rubber mallet to pound the clay into submission :)

Wyndham

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Biglou13    202

This is the Texas tile press but I did mine for about $20 with a wood frame, air tubing and a compressor I had from HF.

Mine work fine for about 200 pressing before I made another mold.

Wyndham

.

Any pics

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Wyndham    98

no I'm afraid not but the Texas tile press site videos and tutorial will give you about everything you need.

I used a moist, freshly slabbed clay as the master. built a  frame 10 in on a side with 1x4 pine. These 2 things replace the metal frame and silicone rubber master he used.

Hope this helps. If anything else just let me know.

Wyndham

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Mug    49

Smooth-on 121-50 wet is a good easy to use urethane rubber. The wet has a mould release built in.

All in all you want to use the cheapest molding material that gets the job done for its intended use.

Some urethanes have a short lifespan, it is all in what you want from your mold.

The harder your mold the more clean and basic your detail will need to be. You can make a mold from hard plastic if it has no under cuts.

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Stephen    139

Thanks mug, I will check that out. I am assuming I will need to use the master rubber model every so often to make new working molds as they wear out and do want those models to be useable for years if possible spending the vast majority of that time stored away in a cabinet. 

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