RTV silicone thickening agent help

airair

Sr Member

• Sep 14, 2012

• #1

hi,

ive got some rtv silicone thickening agent, but am not sure what the process is when mixing it.

i understand that you add it to the plain white rtv silicone liquid before you then add the catalyst to the silicone.

but on the instructions it it says "It is recommended that the first few coats should be applied with un-thickened RTV to assure highest detail."

but im not sure if that means a coat of the plain unthickened white rtv by itself or rtv plain unthickened mixed with some catalyst?

 

I

IEDBOUNTYHUNTER

Sr Member

• Sep 14, 2012

• #2

Mixed with catalyst. Or it wont cure. Always use cat

 

nachtinis

Well-Known Member

RPF PREMIUM MEMBER

• Sep 14, 2012

• #3

IEDBOUNTYHUNTER said:

Mixed with catalyst. Or it wont cure. Always use cat

Click to expand...

Yep, what we are talking about is called the "print coat".

Basically, a thin layer of rubber is brushed onto the model which allows for finer detail to be captured, then you can finish the rest of the mould with a higher shore or thickened rubber as needed.

 

airair

Sr Member

• Sep 14, 2012

• #4

great thanks for the info

i was confusing myself there!

so if i mix my silicone with catalyst, then take a bit, and brush on a thin coat, or at least cover the whole mould.

then add in the thickener to my mix and then brush that all over the top.

that sounds good now.

ive decided to do brush on, as my part is very curved, and to save silicone on both sides, i think brush on is better, as i can then layer some modroc plaster ontop to form a strong shell.

then turn over the mold, and finish the second half of the mold with more silicone and modroc plaster shell.

cheers guys

 

nachtinis

Well-Known Member

RPF PREMIUM MEMBER

• Sep 14, 2012

• #5

Be sure to let you print coat cure first before you do the reinforcement rubber.

 

airair

Sr Member

• Sep 14, 2012

• #6

nachtinis said:

Be sure to let you print coat cure first before you do the reinforcement rubber.

Click to expand...

so for the first unthickened coat, i should just mix a very tiny amount, enough to cover my mould,brush it on,and let it cure.


then make a new fresh mix with thickener and do the second coat?

how long usually should you wait for a think coat to cure?

i think the pot life is usually 30 minutes once you've mixed catalyst and silicone.

this will be the first time im using this thickener, so i hope i don't cock it up!

 

nachtinis

Well-Known Member

RPF PREMIUM MEMBER

• Sep 14, 2012

• #7

airair said:

so for the first unthickened coat, i should just mix a very tiny amount, enough to cover my mould,brush it on,and let it cure.

Click to expand...

Yes

airair said:

then make a new fresh mix with thickener and do the second coat?

Click to expand...

yes

airair said:

how long usually should you wait for a think coat to cure?

Click to expand...

Sometimes thickeners can speed the cure process up, but read the packaging about the cure time to get an idea of how long you need to wait.

airair said:

i think the pot life is usually 30 minutes once you've mixed catalyst and silicone.

this will be the first time im using this thickener, so i hope i don't cock it up!

Click to expand...

Basically the rubber will need to cure to be tacky to the touch, some rubbers cure faster than others.

As a test you can put some in a cup and test that as you wait.

With products like rebound and dragonskin, I usually wait about 6 hrs before i do anything to my print coat.

Typically i do my moulding before bed and before i go to work in the morning. They all turn out pretty good.

 

NormanF

Master Member

RPF PREMIUM MEMBER

• Sep 14, 2012

• #8

There are some videos on YouTube by SmoothOn that demonstrate the process. It should be similar for rubber from other manufacturers. And be sure you make the mold thick enough! I wasted a lot of rubber and shell material because the first one I made was too thin. I use Rebound25 and it should be 3/8 of an inch thick.

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