Flexible mold material

[BlindSquirrel]

I am in the molding stage with several projects, a few of them quite large. My frustration is that many of the liquid silicone and rubbers used for molding are FRAKKING expensive, especially on a large scale.

Any recommendations on an economy approach to this problem? Am I better off going with a brushable rubber with a plaster mother mold or is there something else I can use?

 

[rockas78]

<div class='quotetop'>QUOTE(BlindSquirrel @ Dec 6 2006, 10:39 PM) [snapback]1372892[/snapback]</div>

I am in the molding stage with several projects, a few of them quite large. My frustration is that many of the liquid silicone and rubbers used for molding are FRAKKING expensive, especially on a large scale.

Any recommendations on an economy approach to this problem? Am I better off going with a brushable rubber with a plaster mother mold or is there something else I can use?
[/b]

Hi,you can use a thin layer(this way you dont get airbubbles) of the (expencive silicone)when this start to set you can add to another batch of the same silicone with a thixotropic agent,this is a thickening agent for silicone,then you can brush it or spatulate the thick silicone over the thin layer.This way you can make a mold very easy.Dont forget to use a silicone with shore up to 35 for large projects.
What silicone you use?

Nikolas

 

[BlindSquirrel]

<div class='quotetop'>QUOTE(rockas78 @ Dec 6 2006, 03:47 PM) [snapback]1372896[/snapback]</div>

What silicone you use?

[/b]

I just used Smooth-On Oomoo-30 for a smaller project and was horrified to see how little I was able to accomplish with a $30 kit. I've got pieces 10 times bigger that need molding but can't afford a proportional price....

I've never tried the brushables...that may be my only option.

 

[rockas78]

<div class='quotetop'>QUOTE(BlindSquirrel @ Dec 6 2006, 10:51 PM) [snapback]1372900[/snapback]</div>

<div class='quotetop'>QUOTE(rockas78 @ Dec 6 2006, 03:47 PM) [snapback]1372896[/snapback]

What silicone you use?

[/b]

I just used Smooth-On Oomoo-30 for a smaller project and was horrified to see how little I was able to accomplish with a $30 kit. I've got pieces 10 times bigger that need molding but can't afford a proportional price....

I've never tried the brushables...that may be my only option.
[/b][/quote]
For small projects you need soft and for large hard,what you use is for medium projects.Dont forget to use yellow petroleum to make the surface smoother.Also for large scales make a fiberglass core on the outside not plaster because its heavy.
Nikolas

 

[quadmasta]

Dont forget to use yellow petroleum[/b]

You're not supposed to get petroleum byproducts on silicone.

 

[Hacksaw44]

quadmaster is correct,and don't use rubber it will shrink.Silicone is the best approach.

 

[replicaprops]

For a large mold use smooth-on brush on http://www.smooth-on.com/brush-on.asp
or dragon skin with thickener.

http://www.smooth-on.com/silicones.asp#dragon
Thi-Vex™II Silicone Thickening Agent


THI-VEX II is made especially for thickening Smooth-On’s Mold MaxÔ 10, 20 & 30 (tin-catalyst), Smooth-Sil 920, 930, 940 & 950 (platinum-catalyst), Dragon Skin or Ecoflex (platinum catalyst) silicones for vertical surface application (making brush-on molds). Different viscosities can be attained by varying the amount of THI-VEX II. Read the Technical Bulletin for full details.

Pint = 1 lb. = $13.39

 

[clonesix]

<div class='quotetop'>QUOTE(rockas78 @ Dec 6 2006, 10:56 PM) [snapback]1372908[/snapback]</div>

For small projects you need soft and for large hard,what you use is for medium projects.Dont forget to use yellow petroleum to make the surface smoother.Also for large scales make a fiberglass core on the outside not plaster because its heavy.
Nikolas
[/b]

:confused WHAT?


BlindSquirrel,

Yes, silicone is expensive. A cheaper alternative is a urethane molding product. I don't like urethanes as well as the silicone. You get what you pay for. IMO, silicone is worth its weight in gold.

It would help if you would include a picture of the project, or at least a description and size comparison.

The economical method (as mentioned above) is a layer of silicone (.25" - .5" thick) backed up by a more solid material, either gypsum or fiberglass. This is done in several brushed on coats of silicone. The first coat, the "beauty" coat, is brushed on and gets into all the nooks and crannies. After that sets, a second batch of silicone is mixed with a thickener and then brushes on to add bulk to the silicone. Let that set. Add a 3rd layer of silicone and thickener to get any thin spots and to add keys. KEYS ARE VERY IMORTANT.

Keys are little blocks of silicone that are cast, or cut up chunks of cured silicone. They do two things: 1. locate the slicone back into its jacket, and 2. hold the silcone firmly to the jacket.

After you have covered everything with a good half inch of silicone and added keys all over the place, and it is all set up, then it is time to add a solid backing jacket of gypsum of fiberglass to help the silicone hold its shape.


As a rule of thumb, If you are going to make 3 parts or less from this mold, use urethane. If you will make more than 3 parts from this mold, use silicone. I know it is $100/gal, but it is worth every penny. You can buy a 5 gallon bucket for $400, that is $80/gallon. Not bad. You be the judge.

 

[rockas78]

Now you are a little confused by the wise guys :love
Everyone stop to be negative comments in new peoples comments and you may learn something,petroleum is the right solution for smoothening,if you want to buy a( special material) from smooth on or other company and pay 100$ for nothing do it ,im telling the cheapest and best solution.I work with silicones for 12years now and i have used 30 different types of silicones.
This guy try to find a way dont confuse him. :angry
If anyone want pictures on how to mold or something else let me know.



Nikolas

 

[rockas78]

And dont forget,dont use platinum cure silicones because they are very difficult to work with,they need experience and they are very expencive. :angel

If you could send me a pictures on what you want to mold i believe i can help.

my email is ndresios@otenet.gr

Nikolas