Thinning silicone

[robalo01]

Is it possible to thin common household silicone with sillicone oil (used to thin RTV silicone) in order to pour it over a model for mold making?

[mangeboy79]

Is it possible to thin common household silicone with sillicone oil (used to thin RTV silicone) in order to pour it over a model for mold making?

maybe some usefull way to thin it

http://www.youtube.com/watch?v=MCsaKSbZL60

[Vodkaman]

Anything other than a thin coat of regular one part silicone, is going to take forever to set.

Dave

[mangeboy79]

Anything other than a thin coat of regular one part silicone, is going to take forever to set.

Dave

are you sure ? there was a mouldmaking tutorial on this page before the crash with one part silicone

[Downriver Tackle]

I'm pretty sure silicone oils and curable silicones are two totally different materials. A little stinky, but most silicones are reducible with toluene.

[KcDano]

You can rapid cure regular silicone with the addition of water.

[jrav]

Go to the Smooth-on site or get in contact with Del (Del-mart) from this site for the good stuff. The "water added" technique works with certain household type of sil, but it can be MEAN! Gives off a great deal of acid and you have to work pretty quickly before it starts to set up. I always got half-arse molds with it, lots of little pores and inconsistencies due to air/water pockets in the mold.

The blue stuff IS expensive, but it looks like the way to go for any level of quality. Always remember the learning curve with regard to price...you'll go through quite a bit of the household stuff learning how to use it and get a decent result. The expensive, pourable stuff is made for the purpose in your inquiry and likely will be alot easier and cost efficient in the long run.

Sometimes, trying to save money is a more expensive PIA...at least it has been for me at times.

http://www.del-mart.com/shop/home.php?cat=335

Edited December 22, 2008 by jrav
edited to find&post Del-Mart link for silicone/product advice

[robalo01]

The RTV I get here in Mexico is thinned with what they call "silicon oil". I have tried it but: either you pur it stight and it seta fast and is very tough and porous; or, you thinn it with the oil, it turns out a lovely mold that is s little more firm than jello. it won't hold it shape under the presure of expanding foam. So I've been making some molds with regular silicon activated with water.

I guess this is one I'll have to try myself. I'll let you know how it goes.

PS. What about pouring molds with PVC plastisol with a lot of hardener?

[fishcrazy]

You can thin down silicone with naptha but I dont know if you could get it thin enough to pour but if you are looking for something to hold up against the pressure from the foam you could cast your mold with silicone or rtv and then pour a support cast using plaster of paris or smooth-on 300

Mike

[mark poulson]

How about making the mold with your soft silicone, then making a slave casting out of bondo, and then a mold of that out of bondo. Bondo is hard and tough, and if you make a shallow wood box, or can find a shallow plastic dish that's the right size, you should be able to make a mold that will last for lots of castings. depending on what you're casting with, use the appropriate release agent. The manuf. of your casting material should be able to steer you to the right releas agent.

And you'll have the bondo slave to make more molds if you need them.

[Spike-A-Pike]

are you sure ? there was a mouldmaking tutorial on this page before the crash with one part silicone

The Slip Mold tutorial is a downloadable pdf file in the hard bait How-To forum. Thanks again CrawChuck for writing it.

[Nela]

I live in california where naptha, mineral spirits, and toluene are banned so I use a product from my local hardware store called "painter's solvent" by olean strip. (Which by the way is very easy to mix)  It's a replacement for MEK, TOLUENE, XYLENE, TURPENTINE, AND VM&P NAPHTHA so my guess is you can use any of those mentioned. Before that I had tried 100% acetone it works a little bit but didn't give me the "liquid" consistency I required in order to pour silicone into the object I was wanting to old using rtv silicone from siliconedepot.com Now using the first method mentioned I am able to create any mold for my cement, resin (epoxy), or plaster of paris. 

 

ps curing time is not more than 24 hours

[Anglinarcher]

WOW, this is an interesting and strange thread.  I have used vinegar to thin household silicone, but never to make a mold.

I have used silicone oil to recondition and lengthen the life of Alumilite silicone molds, and that works well.  I have added silicone oil to reduce the hardness of some of their silicone mold material when making it, but I am not a fan of doing that.

I suspect that each silicone material and supplier requires their own method so any answer we give will be product specific.

[eastman03]

It is a strange thread lol.  

To make a quick and dirty test mold, i have used 100% silicone caulking.  I followed some random youtube demo.  I added water and some soap i think lol.  I mixed it all up with gloves on (very stinky).  Then i sort of forced it and pressed it around my master.  It did work, although with imperfections.  I would never choose this for an actual mold, but here in manitoba, that stuff is bloody expensive.  Especially if I want to mold a larger lure.  

Anyway, it worked and I make a couple large paddle tail tails for a hybrid lure.  I'm glad I did it that way, as a test, because I need to make a few tweaks to improve it before I would make a good mold.   

[mark poulson]

7 hours ago, eastman03 said:

It is a strange thread lol.  

To make a quick and dirty test mold, i have used 100% silicone caulking.  I followed some random youtube demo.  I added water and some soap i think lol.  I mixed it all up with gloves on (very stinky).  Then i sort of forced it and pressed it around my master.  It did work, although with imperfections.  I would never choose this for an actual mold, but here in manitoba, that stuff is bloody expensive.  Especially if I want to mold a larger lure.  

Anyway, it worked and I make a couple large paddle tail tails for a hybrid lure.  I'm glad I did it that way, as a test, because I need to make a few tweaks to improve it before I would make a good mold.   

I have found that applying a thin coat of the 100% silicone over the master, spraying water over that, and then adding additional silicone and water mixture to fill the mold box works.  The silicone/water mixture sets overnight, and the pure silicone layer after another 24 hours.  That way I was able to preserve the details on the master, and still have the silicone mold set up faster.  I tried just using pure 100% silicone all the way, and it took two weeks to cure.

[bogdan_alex]

the problem I discovered is that RTV silicone has a great amount of shrinkage. The mold is only usable for a more limited period of time....then the differences becomes too obvious. I think that's because the core of the mold is still curing for a long time if it's too thick. And you have to be careful the RTV does not stick to your master. The molding silicone does not stick on anything but silicone but RTV does.

I only use gasket RTV (+300C..the red one) to make molds for lead pouring and it's working pretty nice.

 

[wchilton]

I've used silicone oil to thin two-part RTV silicone and it works but the cured silicone is softer.  I think the oil just acts as a plasticizer to make the cured product softer/more flexible.  You can reduce your mold making costs by chopping up old/reject silicone molds and using them to fill space around the cavity.  I just make sure and pour new silicone around the master to get a smooth surface.  To chop up old molds I use a food processor.  Cut old mold into about 1-inch  chunks and add enough silicone oil (just enough to coat surfaces) to keep chunks from sticking together while being chopped up.  Mix up the 2-part RTV before adding chopped silicone.