<p>Would a two step process work? Make the first mold off of the fiberglass with latex rubber (or another molding rubber that is not anti-fiberglass) then make a plaster positive from that. So now you have the fiberglass form in plaster, use that for the silicone mold.</p>

CC BY-SA 4.0
2018-08-09T17:02:37.790Z
sounds like an interessting approach - what kind of molding rubber would you suggest for a life size statue that would can keep the form and isn't too expensive?
Frezzley
CC BY-SA 4.0
2018-08-10T15:17:56.070Z
You should check out the mold making materials manufacturers or retailers for that. https://www.sculpturehouse.com/ and https://shop.smooth-on.com/ have a lot of info.
rebusB
CC BY-SA 4.0
2018-08-09T17:00:00.150Z
2018-08-09T17:00:00.150Z
rebusB
<h2>Just use a tin cured silicone.</h2>
<p>fiberglass and tin-cured silicone work fine, I use fiberglass over-molds (mother-molds) for silicone molds.</p>
<p>It is only platinum based silicons that have problems, anything that contains even trace amounts of sulfur prevents it from curing, fiberglass included.</p>

CC BY-SA 4.0
2020-08-20T18:42:12.383Z
Interessting, I'll give it a try
Frezzley
CC BY-SA 4.0
2020-08-18T04:22:12.623Z
2020-08-18T04:22:12.623Z
John
<p>I have an fiberglass object, that I want to make a mold of.
Commonly known is that fiberglass and silicone don't like each other.
And when I tried to make the mold, I experienced what I expected got a gooey consistency.
I believe this phenomenon is called cure inhibition.</p>

<p>Is there a way that I can make it work?
Or is there a different material that would work (soft molding material)?</p>

CC BY-SA 4.0
2018-05-13T18:55:11.550Z
Did you by any chance use air curing silicone from a tube like the stuff for sealing bathtubs?
Nothingismagick
CC BY-SA 4.0
2018-05-13T21:50:13.890Z
How close of a match do you need.  If you applied a layer of smooth saran wrap to the original and then pour silicone of that, would the variance caused by the thickness of the wrap be too much for your intended use?
Henry Taylor
CC BY-SA 4.0
2018-05-14T05:46:39.237Z
@nothingismagic no im used a 2 component silicone from smooth on
Frezzley
CC BY-SA 4.0
2018-05-14T05:47:59.107Z
@HenryTaylor the difference in depth wouldn't make a difference however I guess I would be having a hard time getting the details right
Frezzley
<material-selection><mold-making>
How to make a silicone mold of a fiberglass object?
Frezzley
# How to make a silicone mold of a fiberglass object?

(Asked by: username_0 on 2018-05-12)

I have an fiberglass object, that I want to make a mold of.
Commonly known is that fiberglass and silicone don't like each other.
And when I tried to make the mold, I experienced what I expected got a gooey consistency.
I believe this phenomenon is called cure inhibition.

Is there a way that I can make it work?
Or is there a different material that would work (soft molding material)?

**Tags:** material-selection, mold-making

> **Comments:**
> **username_1**: Did you by any chance use air curing silicone from a tube like the stuff for sealing bathtubs?  
> **username_2**: How close of a match do you need.  If you applied a layer of smooth saran wrap to the original and then pour silicone of that, would the variance caused by the thickness of the wrap be too much for your intended use?  
> **username_0**: @nothingismagic no im used a 2 component silicone from smooth on  
> **username_0**: @HenryTaylor the difference in depth wouldn't make a difference however I guess I would be having a hard time getting the details right  

---

## 2 answers

### Answer by username_3 on 2018-08-09. Score: 2

Would a two step process work? Make the first mold off of the fiberglass with latex rubber (or another molding rubber that is not anti-fiberglass) then make a plaster positive from that. So now you have the fiberglass form in plaster, use that for the silicone mold.

> **Comments:**
> **username_0**: sounds like an interessting approach - what kind of molding rubber would you suggest for a life size statue that would can keep the form and isn't too expensive?  
> **username_3**: You should check out the mold making materials manufacturers or retailers for that. https://www.sculpturehouse.com/ and https://shop.smooth-on.com/ have a lot of info.  

---

### Answer by username_4 on 2020-08-18. Score: 1

## Just use a tin cured silicone.

fiberglass and tin-cured silicone work fine, I use fiberglass over-molds (mother-molds) for silicone molds.

It is only platinum based silicons that have problems, anything that contains even trace amounts of sulfur prevents it from curing, fiberglass included.

> **Comments:**
> **username_0**: Interessting, I'll give it a try  

---

