Moldmaking Mould/bubble gates.

Sometimes mine stay on if I just use clay. Other times I drill a small hole and use wire + clay to form the gate. Could also glue them on. Or if they are not sufficiently open due to displacement after pouring silicone, you can always cut them bigger, or cut them so that they function.

If you pour the silicone carefully and just let it rise, it should not disturb the clayed-on vents but rather hold them in place, increasingly as it rises. If they do come loose while pouring silicone, it's not a huge deal because you can always cut more vents after it's cured. But maybe test the mold first to see if cutting more vents prove necessary.

You can always use a tool to smooth the edges of the clean clay and reshape so it won't just form blobs of resin that you have to cut off. Or you could use a small drop of glue for each one instead of clay.

 

Wow that is a lot of gates. I bent my wire at an angle and pierced my sculpt to keep the gates on, but I put them more on the inside of the head rather than the edge where the 2 head pieces come together. I did have some complications with the pour holes I made which made removing the 2 sides difficult, so keep that in mind how the sides are supposed to be removed.

To help keep my vents straight or from accidentally toppling over I used some thin strips of blue tape along the top out of range of what the silicone rubber will be poured.


Silicone Rubber Mold for BJD Head by Mothi03, on Flickr

That should give you an idea how I kept them together. I need to rethink gates for my next head attempt though. So please excuse the mess.

 

I always say: if in doubt, more is better.
There have been times that I have poured into vents to make a good casting.
You can ask questions until you are blue in the face.
Keep good notes (I never had the luxury of digital cameras when I was learning).
You will learn more from your own mistakes than from any answers from a forum of people who are not there.
The keyword is: THINK.
Finally, read and re-read everything twigling posts (she is sharing more than anyone here.).
Also, read between the lines.

Have Fun !!!


(PS: Isn't this forum transition, the shits?)

 

Had another could of thoughts;

instead of using clay to attach your vents, you could carefully drill holes that are the same size as the vent-dowel you're using and insert the dowels rather than try to glue them on. Also with regards to removing sprues, it is always easier to do so before the resin has completely hardened. I don't mean you should demold too early, but before it is completely set and rigid it does remain flexible for a while and during that time it is easy to cut or trim. After fully hardening, some gentle scraping with a fine, flat file will also help. If the filing is on an external surface, you'd need to follow up with sandpaper etc.

 

I used simple hot-glue. It worked fine and didn't prevent the silicone from setting.

My experience is that more vents isn't always better. For one, it will take you much longer to finish the resin part, because you'll have to sand more. Usually it's enough to place gates at the highest points of your mold and anywhere where there's a lot of detail where airbubbles could get trapped (like ledges or keys). You could always add vents later, by carefully drilling the mold.

Also, depending on where the pouring-gates will be, I'd place the ear-vents a little differently. Seems to me that the ear's edges are where air could get trapped, because of the detail there.

 

Could you tell me where you want to put the pourgate? It's not so much the slope I'm worried about, but the jagged edge (easy for bubbles to get stuck). Then again, if you pour slow, it could very well be that there won't be any bubbles and if you tap the mold after pouring resin in it, you can get rid of airbubbles as well.

 

I don't see why the tips of the ears would get bubbles, they are not at a high point in the mold.

I wouldn't use hot glue as it would have the same blobbiness as a bit of clay would. I'd use superglue.

 

Oh, ok. No, then I don't think the ears won't be a problem. Never mind what I said.

@twigling: I mean superglue, not hot glue. Duh.