Mould Making... an attempt at

[oldskoolrebel]

Having just returned from BLAM, I decided to sort though the various projects I have on the go. My plan over the next couple of weeks is to downsize. I'll be working on one or two projects at most. I may well be selling stuff in the Bazaar, so keep an eye out.

Anyway, they easiest project to continue working on just now is my ongoing pulp project.

So over the last wee while I've been meaning to make moulds of some of my egyptian ruins. So today I had a shot of pouring the mould. I've never done this before, and I am a bit concerned about the number of air bubbles appearing on the top. I suspect that these may run through the entire mould! Damn!



What do the more experienced mould makers think? Any tips for future?

Kind Regards
Andy

[Elk101]

Andy, I'm sure there is a thread somewhere about this very topic. I can't for the life of me remember who it was though. They built an agitator for it to reduce the air bubbles
 It was basically a vibrating plate.

[oldskoolrebel]

Andy, I'm sure there is a thread somewhere about this very topic. I can't for the life of me remember who it was though. They built an agitator for it to reduce the air bubbles
 It was basically a vibrating plate.

I'll have a quick wee search and see what else I can fine!

Cheers
Andy

Edit- Immature laugh, vibrating plate

[DELTADOG]

You can relax, those bubbles are really normal on the surface of a mold. Blow over the mold to make them collapse, that new one can reach the upper surface before the silicone begins to cure. Repeat this till no more bigger bubbles will come up and your mold will be fine.

[Elk101]

I'll have a quick wee search and see what else I can fine!

Cheers
Andy

Edit- Immature laugh, vibrating plate

Yeah, just Google "vibrating" and "bubbles" and you'll be fine.

[grant]

Yeah, just Google "vibrating" and "bubbles" and you'll be fine.

 

[Dewbakuk]

Yep, what deltadog said.

[Elk101]

Yep, what deltadog said.

Funnily enough I just did a quick search and found replies you'd made to a similar query years ago!

I found this discussion from Hirst arts too:

http://hirstarts.yuku.com/topic/4434/Vibrating-Table-vs-Vacuum-Chamber-vs-Pressure-Chamber

No idea if it helps though?

[tin shed gamer]

This looks more like you've been overly concerned about mixing the silicon ,(mixing it briskly more haste less speed)and pouring it to fast., it's possible to build a near vacuum chamber for under £30, which will do for DIY projects.
Mark

[6milPhil]

As Tin Shed says you could build your own vaccuum chamber or pressure pot very cheaply to see how you get on with casting. My first chamber was made from an old pressure cooker. I wouldn't bother with a vibration plate.

Without one you should try pouring slowly into the mould box, preferably into one spot not too close to the master. Seeing as you're using Lego for boxes you could build in a pouring spout so it gently trickle down the box wall. 

Also pour a small amount in to start and perhaps swish it around gently.

Of course any approach can change depending on the master. The learning curve for casting isn't too steep, you will suss it eventually but be prepared for a roller-coaster of emotions on the journey. 

[Zaheer]

What works for me is painting a layer of silicon onto the master itself, then pouring the rest of the silicon into the mould. Haven't had any problems with bubbles since doing this.

[tin shed gamer]

I was going a little more low tech,
You make a box to what ever size you need(just not wood)I use heavy duty plastic sheet with a lid,and add a thin layer of rubber around the top( inner tube works well)and attatch,a break bleading hand pump to the side ( these you can pick up for around a tenner)I normally build one when I've an odd shape to mould.
Its a simple project and a throw away tool .
Mark.

[NurgleHH]

Yeah, just Google "vibrating" and "bubbles" and you'll be fine.

Elk101: Being honest Steve, I don't want to do this. Sounds like very dirty things. 

But I think before pouring it to the mould you can also use an old mixer (low intensity) to get the air out of the material. Bakers do this often for special cakes. Some bubbles will only stay.

[Elk101]

Elk101: Being honest Steve, I don't want to do this. Sounds like very dirty things. 

Dirty? It hadn't occurred to me. It must be your movie experience rubbing off! 

This is of interest as I've always been put off trying to make my own resin stuff due to the perceived need to build something like a vacuum chamber. Would something like a dental plaster have the same issues?

[6milPhil]

This is of interest as I've always been put off trying to make my own resin stuff due to the perceived need to build something like a vacuum chamber. Would something like a dental plaster have the same issues?

Yes to a degree, but it does depend greatly on the master. If you're making a fill mould of a pyramid that's a lot easier to cast than a cube which in turn is easier to cast than a rhombus, and so on.

Before I had a chamber I cast successfully with just plasticine and dental plaster, and also press moulds, but it wasn't anything complicated.

The benefits of vacuum/pressure are reliablity and the speed from that, it's like cutting your lawn with an electric mower, but you could use a scythe.