Mould making newbie messy mistake

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Agent Orange
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Mould making newbie messy mistake

Post by Agent Orange »

Hi all,

I was trying to make a silicone mould of a large car part - I've had some really good results from making small scale stuff, so I thought I'd try my newly formed skills on a bigger project.

I think I used too much catalyst as the finished mix was quite dark in colour but now it won't set and is like a mushy gum.

Its an expensive mistake to make but I guess you have to speculate to accumulate but I'm not sure how to clean my master.

Would catalyst be a good way to get uncured silicone off my master? Any tricks of the trade?

Many thanks,

Steve
"You Klingon Son, you killed my Bastard!"
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Ziz
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Post by Ziz »

I'm guessing you tore it apart already because you're trying to clean off the master. Maybe you used too little catalyst and it needed to sit longer? Also, how old is your rubber & catalyst? If it's been sitting a while, it actually does get "stale" - not to where it's unusable but enough that it takes longer to cure and sometimes doesn't cure properly.

As for cleaning the master off, go with the standard paint stripper techniques - Simple Green or oven cleaner spray.
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Agent Orange
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Post by Agent Orange »

Thanks Ziz - yes, I have ripped it up already.

I gave it 72 hrs to set, I intended to set it aside until I got (or could afford to get) some more silicone, then today I noticed the mixing bowl I used hadn't cured as I went to clean it out.

Maybe it was for the best as i can see i've made a few mistakes in the design of the mould - a little less haste next time and hopefully, cost!

You could be right about not enough catalyst - actually, I have done just that as I've just re-read the instructions - argh, what an idiot!

Steve
"You Klingon Son, you killed my Bastard!"
Styrofoam_Guy
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Post by Styrofoam_Guy »

I once made a mould and the rubber didn't set in the time the instructions said it would (24 hours). I took the rest of the RTV back and got a replacement.

I was not looking forward to cleaning up the master so I left it. I don't know if I had a bad batch or did not mix in enough catalyst but the thing actually cured after over a week. I lucked out that times.

Unfortunately recently I had a mould that would not cure even after leaving it for 2 weeks and putting in a warm spot hoping the heat would speed up the curing process. I am guessing the RTV rubber was old.
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Ziz
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Post by Ziz »

Agent Orange wrote:Thanks Ziz - yes, I have ripped it up already.

I gave it 72 hrs to set, I intended to set it aside until I got (or could afford to get) some more silicone, then today I noticed the mixing bowl I used hadn't cured as I went to clean it out.

Maybe it was for the best as i can see i've made a few mistakes in the design of the mould - a little less haste next time and hopefully, cost!

You could be right about not enough catalyst - actually, I have done just that as I've just re-read the instructions - argh, what an idiot!

Steve
What exact rubber/catalyst did you use - what brand/specs? I use Smooth-On MoldMax 30. It has a 10-1 ratio so I do all my measuring in metric rather than imperial. Their OOMOO line is 1-1 mix ratio of two equal parts of different halves of rubber (as opposed to rubber/catalyst) but it's about 50% more expensive than MoldMax. For personal occasional use, it's fine but for perpetual use like I need, it adds up to a lot of extra cost.
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http://www.modular-models.com
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____________________________________
"The customer that spends the least complains the most."
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