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Old 09-20-2017, 10:27 AM   #1
sipuli
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Silicone mold problem

Hi,

I have troubles in making silicone mold (Rebound 25) from my sculpture (Chavant NSP) and I basically can't proceed any further at the moment.

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Silicone works like a charm, no issues with that. The problem is the hair/braids, see picture below.

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Luckily I tested small portion of the braids. Silicone is getting literally into all cavities and underneath the braids and so when I'm trying to get mold off braids come along and silicone mold is looking just crazy, see picture below.

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So my question is: any ideas how to get clean mold and little as possible damage the original sculpture?

At the moment I don't use any mold releases, just thinking if spraying some would help a little?

One option I'm thinking would be to thicken already the first coat of Rebound 25 for the braids so that it would not get to all holes.

Also, If there would be some material that i could apply on top of the braids and then rub almost all off, so that the material would get off from top of the surface but would stay into cavities (sort of like dry brushing) and underneath braids so that silicone then wouldn't. Any ideas for such a material?

Thank you very much,
Sami
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Old 09-21-2017, 05:18 PM   #2
QX403
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Quote:
Originally Posted by sipuli View Post
Hi,

I have troubles in making silicone mold (Rebound 25) from my sculpture (Chavant NSP) and I basically can't proceed any further at the moment.

Attachment 108190

Silicone works like a charm, no issues with that. The problem is the hair/braids, see picture below.

Attachment 108191

Luckily I tested small portion of the braids. Silicone is getting literally into all cavities and underneath the braids and so when I'm trying to get mold off braids come along and silicone mold is looking just crazy, see picture below.

Attachment 108192

So my question is: any ideas how to get clean mold and little as possible damage the original sculpture?

At the moment I don't use any mold releases, just thinking if spraying some would help a little?

One option I'm thinking would be to thicken already the first coat of Rebound 25 for the braids so that it would not get to all holes.

Also, If there would be some material that i could apply on top of the braids and then rub almost all off, so that the material would get off from top of the surface but would stay into cavities (sort of like dry brushing) and underneath braids so that silicone then wouldn't. Any ideas for such a material?

Thank you very much,
Sami
You'll need to use mold release on areas like that or some kind of agent like baby oil or vasaline watered down (depending on the medium you're using) so the silicone doesn't stick into fine pieces and crevices. Thickening won't really change much. I've heard of people even using crisco baking spray.

Looks like an avatar character, looks good.

Also is your statue fully dried if using air dry medium or did you bake it? It doesn't look dry or set up to me in the pictures.
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Old 09-27-2017, 02:47 AM   #3
rgm501
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It's not about using mold release, silicone won't stick to the clay.
The problem is with the sculpt itself.
You have to options,

1, cut the hair off and work out a key system and mold n cast the hair seperatly.

2, get rid of the gabs, all the nook and crannys that the silicon can get into.
If you don't and you still manage to get the sculpture out of the mold, once you try with resin, the rest will not have as much give and flex and if will tear the silicone when trying to remove the cast.

Hope that helps.
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Old 10-08-2017, 06:09 PM   #4
Bobfrog
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What is your eventual plan out of interest - are you going to cover the bust completely and then build some sort of plaster case around it?

I assume that you are going to work it so that you do your resin pouring from the base downwards. If so you just need to make sure you have a vent around the chin area so that you don't get air trapped in the cavity there.

Good luck - sculpt looks great.
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Old 10-24-2017, 03:35 PM   #5
sipuli
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Many thanks for replies guys! Im filling the cavities right now. Quite tedious and slow process but its getting there.

Quote:
Originally Posted by Bobfrog View Post
What is your eventual plan out of interest - are you going to cover the bust completely and then build some sort of plaster case around it?

I assume that you are going to work it so that you do your resin pouring from the base downwards. If so you just need to make sure you have a vent around the chin area so that you don't get air trapped in the cavity there.
Huge thanks for your input - Actually Im planning to do rotocast and fill inside with something more cheaper material - any suggestions by the way?. Do you think it would work without a vent that way or do you see any other problems with roto casting?

Thanks!
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Old 12-03-2017, 01:15 PM   #6
Arkalogik
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Quote:
Originally Posted by sipuli View Post
Many thanks for replies guys! Im filling the cavities right now. Quite tedious and slow process but its getting there.



Huge thanks for your input - Actually Im planning to do rotocast and fill inside with something more cheaper material - any suggestions by the way?. Do you think it would work without a vent that way or do you see any other problems with roto casting?

Thanks!
I do a lot of rotocasting and you usually have to do a couple separate pours to get it thick enough for a piece like this. You can add filler like microspheres to thicken it up but 2 pours is much easier and less hassle in my opinion. You need to make a two part mold with a removeable plug where you can refill the mold pop the silicone plug back in. It also all depends on what silicone and resin you are using on what results you will get.
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Old 01-03-2018, 02:35 AM   #7
Bobfrog
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Quote:
Originally Posted by sipuli View Post
Many thanks for replies guys! Im filling the cavities right now. Quite tedious and slow process but its getting there.



Huge thanks for your input - Actually Im planning to do rotocast and fill inside with something more cheaper material - any suggestions by the way?. Do you think it would work without a vent that way or do you see any other problems with roto casting?

Thanks!
Sorry mate, totally missed your reply (been a hectic few months for me).

No worries at all and tbh I don't have any experience with rotocasting (I just do normal casting using a pressure chamber). So you're probably best off asking someone like Arkalogik. From what I know of rotocasting it should easily deal with an area like the chin.

Let us know how you get on
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Old 01-23-2018, 05:00 PM   #8
Viridis
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If it were me personally I would do a few "print coats" with a much thinner silicone first. They'll pick up the fine details and won't leave you with the big bubbles you're getting. Once you have the print coats down build up over those with your thick silicone.

Prepare yourself to lose the braids, that may just be the case. You've got a lot of areas that you're mold is going to grip to no matter how many nooks and cranies you fill. That's why it's important to get your mold right and I can't recommend a print coat highly enough.
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Old 01-27-2018, 09:47 AM   #9
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Mold Max 25 from Smooth on would be a good option for making a mold. The problem is that you will need to fill in all those undercuts on the braids with clay first. Anything that gets stuck when making a mold can be carfully cut out and that extra silicone under braids cut out but is much better to just do with clay first as much as possible. You would also need to make a two part mold with a plug if you really want good casting and not have a hassle with the mold.

Here is an example of a half scale bust I did that was similar in Mold Max 25.
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