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Shake Yer Booty update Jan. 22 Materials: Where to get 'em! |
pdrake
Tiki Socialite
Joined: Jan 13, 2006
Posts: 1764
From: las vegas
|  Posted: 2006-11-29 9:39 pm Permalink
um, as a new caster, i'd just like to chime in.
"vent"???
"huh"??
"der"??
"what"??
help, please.
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VanTiki
Grand Member (5 years) 
Joined: Nov 25, 2005
Posts: 907
From: Hawaii
| Posted: 2006-11-30 10:05 am Permalink
Quote:
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On 2006-11-29 21:39, pdrake wrote:
help, please.
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Aloha - I just got my newest issue of MAKE magazine, and there is a great article on silicone mold making and resin casting. Check it out! MAKE vol. 8
if they don't have it at your local bookstore, order one at:
www.makezine.com
the sister magazine CRAFT is also great
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Bowana
Grand Member (4 years) 
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2006-12-01 07:33 am Permalink
Thanks for the tip, Rum Demon and Mrs. The rainbow vent was to let the air escape from the tips of the pom poms (still waiting to hear the proper term for those things!) but after further examination I realized that the air had nowhere to go. In the vacuum chamber it wasn't a problem, but casting w/o the vacuum there were problems.
I've got the master for this figure pretty much sanded and smoothed to perfection and will make a second mold on it(with revised venting of course!).
Glad ya like the figure so much that you'd take an amputee! They've all gone to their graves though and I'd hate to part with flawed work!
Pdrake: A vent is an escape route for air inside of a mold. When material is poured into a mold it displaces the air already inside of it. A mold of an object shaped like a Tiki mug has a ready made escape route because of the wide aperture of the object (the perimeter of the bottom of the mug). A mold of a shape such as a human figure has a maze of small cavities that the casting material must find it's way into, such as arms, ankles, and the like. Vents in strategic locations throughout the piece help the casting material flow to where it needs to be. I know it's hard concept to grasp from reading about it. Seeing it actually happen will make it much more understandable. Hope this was helpful to you.
Now, as far as "huh??", "der??", and "what??", these are things I say on a frequent basis myself. 
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Clarita
Tiki Socialite
Joined: Sep 26, 2006
Posts: 1234
From: BA Arg
| Posted: 2006-12-01 09:38 am Permalink
Hey Tikidav!It's so cool that you're experimenting here in real time!!I'm so proud of you!And I have a question, are we talking about poliester resin? I thought that it don't catalize at less than 25 degrees (I don't know how you guys measure temperature) Here that gets very cold we needed to put heaters all around or it didn't get solid...Greetings, keep up the great work!
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mundotiki
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Rum Demon
Tiki Socialite
Joined: Jun 20, 2005
Posts: 254
From: Portland, Oregon
| Posted: 2006-12-01 3:17 pm Permalink
You silly person. Yeah, all the rainbow "vent" did was create more air that needs to escape... right into her arm as it happens. It's probably not necessary to make another mold. Just carefully plug up the ends of the rainbow with a smidgen of oil clay. Katie and I are pretty confident that's all you need to do.
No worries about the amputees. I understand the desire to bury "mistakes", no matter how cool they are.
Best of luck,
Joe
Edit: Ah, this wasn't the finished master that you had cast. Got it. Reading AND comprehension. Must remember that.
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[ This Message was edited by: Rum Demon 2006-12-01 15:19 ]
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squid
Tiki Socialite
Joined: Sep 30, 2002
Posts: 1462 | Posted: 2006-12-02 09:26 am Permalink
Quote:
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On 2006-11-29 21:39, pdrake wrote:
um, as a new caster, i'd just like to chime in.
"vent"???
"huh"??
"der"??
"what"??
help, please.
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Hey pdrake, register on this web forum for casting, sculpting, moldmaking info:
http://www.sculpture.net/community/
Second only to TC in my book.
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Bowana
Grand Member (4 years)
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2006-12-02 7:16 pm Permalink
Quote:
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On 2006-12-01 09:38, Clarita wrote:
I have a question, are we talking about poliester resin? (I don't know how you guys measure temperature)
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Clarita: I'm using urethane resin. It's more durable than polyester and sets up in a few minutes. Something else I found out about mixing talc into the resin is that it makes it brittle if too much is added. Gotta be careful!
As far as temperature, I just use the thermometer on the wall. If it's below about 65 degrees, I know the resin will take longer to cure. In the summertime when it's 100+ I know it's going to set off pretty quick.
Quote:
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On 2006-12-01 15:19, Rum Demon wrote:
Edit: Ah, this wasn't the finished master that you had cast. Got it. Reading AND comprehension. Must remember that.
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Rum Demon: You silly person!
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Bowana
Grand Member (4 years)
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2006-12-16 2:56 pm Permalink
Here is the master casting of the figure primered and prepped for final mold making. The venting was done in a different manner this time. Wire was cut, shaped and put in place with Super Glue to represent the vents. Using this method as opposed to cutting vents into the silicone is far more tedious (I Superglued the vents to my fingers plenty of times before I got them to stick where I really wanted them), but is much more accurate. Another advantage is that the wires also serve as guides when cutting the mold open. Always make sure that vents as well as the figure are secured down to the board or else they could float off somewhere after the silicone is poured!
In this picture I've illustrated the path in which the resin will flow while pushing out the air inside the mold.
I put it upside down to better show the position of the mold when in the pouring stage. The resin is introduced into the right foot area of the mold where it will flow directly to the head, arms, hands and out the vents on pom poms and elbows. The elbows are a high spot that could trap air, and the ends of the pom-poms leave nowhere for the air to escape if not vented. The left leg also acts as a vent, so care must be taken to not pour resin down both leg cavities at once.
This vent on the back of the skirt was necessary to let air out also. Since this one is off the separation line (see pencil mark on board) a separate lateral cut must be made to free it from the mold. The pencil mark on the board serves as a guide when cutting open the mold as it transfers to the silicone after it has set. It's very easy to get lost when cutting open molds so anything that can be done ahead of time to make it easier is a good idea.
More pictures later as the process progresses.........
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finkdaddy
Tiki Socialite
Joined: May 11, 2004
Posts: 2050
From: Wisconsin
| Posted: 2006-12-16 3:02 pm Permalink
This is an amazingly helpful post! I'm anxiously waiting for more info. Thank you for doing this!
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tikigap
Grand Member (8 years) 
Joined: Jan 19, 2006
Posts: 834
From: Arlingtron Virginia
| Posted: 2006-12-16 7:48 pm Permalink
Yeah, this is pretty good. Cant wait to see more.
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Bowana
Grand Member (4 years)
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2006-12-21 9:04 pm Permalink
Thanks guys. Glad you are enjoying it!
The next step is to build a box around the figure to contain the silicone. Any number of materials can be used. Plywood, clay slabs, cardboard, etc. I used some scrap styrene.
I cut the front and back pieces the width of the figure plus about 3/4" on each side. I spaced them about 1/4" away from the front and back of the figure. I then attached them and the two end pieces to the board with hot melt glue.
Make sure the hot melt glue "welds" are pretty beefy so that the box will be sturdy. Check for any small areas that may have been missed. Silicone will find the smallest holes and leak out like crazy.
I regret that I was not able to get any shots of the silicone being poured, but I couldn't do both at once! (I'll have to save that part for another time, but if there's any questions about silicone, go ahead and ask.)
Here is a picture of the filled mold. Notice that I reinforced the attachment of the box to the board with some plaster bandages as a fail-safe method of preventing the box from popping off after it's full of silicone . (It's happened to me before and it's not very pretty!) Also notice the rubber band around the box as added support. Whether or not it needed it I'll never know, but sometimes the weight of the silicone in a full mold will burst open a box that up until that point seemed to be sturdy enough. Better to be safe than sorry!
The silicone must now set for about 18 hours.
More later........
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Bowana
Grand Member (4 years)
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2007-01-01 7:18 pm Permalink
The silicone is set, so now it's time to open 'er up.
The plaster bandages, styrene box, and board are removed leaving the silicone by itself with the figure inside.
The picture on the left shows the bottom of the mold and how the pencil mark described earlier has transferred onto the silicone. This mark serves as a starting point and guide for where the separation line needs to be cut. Also visible are three small dots, which are the ends of the wire vents. These are also used in guiding the cuts. An initial cut with a key knife around the perimeter of the mold is the first cut to be made.
A key knife has a C-shaped, curved blade that will leave a channel in the silicone that will make the two halves of the mold re-align once separated in two. I got this key knife from a ceramics supply company.
Once the key has been cut all the way around the mold, a deeper cut must be made by following the route of the key cut. This next cut will eventually go all the way to the figure inside.
Using an X-Acto knife, the mold is very carefully cut a little bit at a time, while spreading the halves with your fingers. Make sure the cut goes directly (or as close as you can) down the center of every part of the figure, including the vents. Since they are so small, it's easy to cut right past a vent without seeing it. Take your time doing this part. This mold took me about half an hour to open.
As the figure is slowly released from the mold, it will become easier to see where the cut line is to be made. Having a photo or a sketch of the figure is helpful because it's sometimes hard to remember where exactly everything inside the mold is.
When molding a part made out of a hard material (in this case urethane resin) it is sometimes necessary to have to break off pieces of it as the mold is being cut open in order to see where you are going. If you can avoid it or if it's a piece that must not be broken, by all means try to work your way around it. With this figure, it was difficult to see around the base and the first arm as I was cutting, so I had to snap them off. (Sorry about that, Lil' Honey!)
Here is the opened mold and what was left of the master.
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GROG
Grand Member (first year) 
Joined: Jun 21, 2006
Posts: 6180
From: Tujunga
| Posted: 2007-01-01 10:14 pm Permalink
Awesome step by step photos and instructions.Thanks alot. GROG like.
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Rum Demon
Tiki Socialite
Joined: Jun 20, 2005
Posts: 254
From: Portland, Oregon
| Posted: 2007-01-08 10:01 am Permalink
And? And? AND!?... How does it pour?
I've never seen it explained so well in words and pictures. Very nice work. Would have come in handy when I learned this stuff. Despite being able to watch professionals at work, I still could have used graphic explanations of the whole venting process.
Never used a key knife. We were taught to use a surgical scalpel all the way, cutting in tiny zigzags, giving the mold a "diamond" pattern until just before hitting the sculp. This way the whole damn thing is a key. Your way looks easier on the wrist.
Excellent work. Can't wait to see these babies painted and lined up in a row.
-Joe
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Bowana
Grand Member (4 years)
Joined: Nov 10, 2006
Posts: 1117
From: La Mesa, CA
| Posted: 2007-01-09 8:00 pm Permalink
Thanks GROG. Glad GROG like!
Hey RD! I planned another segment showing how the pour works, but I got busy with another thread and this one went cold. I got kinda bored wth it.
I'll have to get back on this one, then!. Thanks for looking!
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