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Tiki Central Forums Creating Tiki Other Crafts Shake Yer Booty update Jan. 22 Materials: Where to get 'em!
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Shake Yer Booty update Jan. 22 Materials: Where to get 'em!
tikigap
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Joined: Jan 19, 2006
Posts: 838
From: Arlingtron Virginia
Posted: 2007-01-09 8:06 pm   Permalink

Yes! Please dont get too bored with it just yet! We're all hangin' on to see what happens! I want to try this and your graphics and explanations are a very useful tutorial! Thanks!


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pdrake
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Joined: Jan 13, 2006
Posts: 1767
From: las vegas
Posted: 2007-01-10 6:40 pm   Permalink

your box is much prettier than mine.



i have to say i don't recommend foam board. i heard that legos were the shizzit. easy up/easy down

oh, well. hopefully it will work out.

what's your move on cutting a mold off of a wood piece you want to save, other than "veddy carefuwy"?



 
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finkdaddy
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Joined: May 11, 2004
Posts: 2061
From: Wisconsin
Posted: 2007-01-10 6:49 pm   Permalink

Quote:

On 2007-01-10 18:40, pdrake wrote:
i heard that legos were the shizzit. easy up/easy down



My neighbor does tons of very high-end, professional casts and he uses logos for almost everything. He also shoves cut-up pieces from old molds into the new mold when he pours it to take up space and use less product. He does the same with the actual resin.
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Bowana
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Joined: Nov 10, 2006
Posts: 1170
From: La Mesa, CA
Posted: 2007-01-10 8:33 pm   Permalink

Tikigap: Glad it's useful to you! Sorry I've been slacking.

Pdrake: All right! You made a mold! Is this your first time? I've not tried foamcore board. How did it work (or not)? Have not tried Legos either. They're probably very sturdy.

My advice on cutting open a mold and not harming the piece is to be vewy cawful! Is it a hook you've got in there? Using a photo or sketch of the piece is extremely helpful as reference. It's easy to forget where everything is when cutting, especially when you have to do it pretty much blind. Take your time. Stop and think if you get lost before you cut any further.

Please post some pictures when you get it open. I want to see how you did. The three most important words to remember are: TAKE YOUR TIME.

Good luck!

Finky: I've also seen people use chunks of cured silicone as filler. I've never tried it myself because of the threat of delamination of the old silicone from the new. I'm too chicken to try it and risk losing a mold (especially one I'm being paid for). How has it been working for your neighbor?



 
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pdrake
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Joined: Jan 13, 2006
Posts: 1767
From: las vegas
Posted: 2007-01-10 8:38 pm   Permalink

it's my second attempt. the first was semi successful. see here . . . . http://www.tikiroom.com/tikicentral/bb/viewtopic.php?mode=viewtopic&topic=21129&forum=7&start=45

i'll be extra careful. this is a moai carved from brazilian rosewood. it looks just like the moai on the cover of the BOT.

foam board, not so good. too thick. it is sturdy, but i think i'm going to invest in legos.

[ This Message was edited by: pdrake 2007-01-10 20:39 ]


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Bowana
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Joined: Nov 10, 2006
Posts: 1170
From: La Mesa, CA
Posted: 2007-01-10 9:12 pm   Permalink

Looks like that one came out of the mold okay?



If the aperature for the pour gate was bigger it would help eliminate air pockets when pouring. You can widen it with an X-Acto. Also, when casting you can tip the mold and rotate it around to burp out any air bubbles. Pour a little, rotate, pour a little more, rotate. Like doing a little dance with it!


 
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Bowana
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Joined: Nov 10, 2006
Posts: 1170
From: La Mesa, CA
Posted: 2007-01-13 10:48 am   Permalink

Here is how I go about pouring a mold such as this.



Things you will need (clockwise from top left corner):
Baby powder (corn starch type) or talc
Silicone spay
Urethane resin (parts A and B)
Resin tint (optional)
Dixie cups
Latex or vinyl gloves
Your mold
thin boards (optional)
Syringe
Rubber bands
Vaseline
Duct tape (optional, and not pictured)

Okay! Got all that stuff?
Unfortunately I was not able to get pictures of every step. I hope these that I do have will be enough. Let's pour!



Some silicones tend to not release the casting as well as others. A shot of silicone release spray on both sides of the inside of the mold will help prevent this. This needs to be done between every few castings or when you feel the castings are beginning to stick.

Allow the silicone spray to dry (5-10 min), then dust the inside of the mold (both halves) with baby powder or talc. This prevents pinhole sized bubbles from occurring on the surface of the castings. I don't know the physics of how it works, I just know that it does! Sprinkle it on, then blow it off to leave a fine dust on the surface of the mold. Do this before each casting.

Carefully align the mold halves and fit them together as in the first picture. Sometimes depending on the size and shape of the mold, a couple of thin pieces of wood are needed to sandwich the silicone to help hold it together. In this case I found that rubber bands were all that was necessary. Duct tape was then wrapped around the top edge of the mold to prevent spillage while pouring (do this only if you are a neat-nut!).

The second picture shows two evenly measured portions of the urethane parts A and B poured into Dixie cups. Some urethanes require measurement by weight, and some by volume, but they are always a 50/50 ratio. Make sure you know which type you have. Be sure to label the cups A and B. (Oh yeah, and put on your gloves)

Prepare the syringe by brushing some Vaseline onto the rubber plunger. Cured resin will stick to it if you don't.



Pour the contents of part A into a separate Dixie cup. I like to add some resin tint to give it some color. Otherwise the castings are white and it's hard to read the surface. Mix the tint into part A until there are no swirlies. Add only a drop. In the picture it looks really dark, but when the resin sets it will be much lighter.

Now add part B to the mix. Mix throughly until no swirlies. Stick the business end of the syringe into the cup and pull back the plunger to fill it with resin. Insert it into the mold cavity and fill the resin at a slow to moderate pace. Sometimes it's good to fill a little bit, then turn the mold slightly on it's side and rotate it, then continue filling. Do this until the mold is full. Urethane has a working time of 5-10 minutes depending on the room temperature so you will have to work quickly. Yeah, I know. Go slow, but fast.



In this case I used a vacuum chamber to cast. The vacuum chamber pulls all the air out of the mold causing it to bubble and froth. (yummy) If you don't have one, you can still successfully cast. Just use the fill and rotate method. I happen to have one, so I use it. I don't want to get into talking about vacuum chamber casting too much because most people do not have them.

The next picture shows how the duct tape contained the spillage. (If you are not using the vacuum it probably will not be this messy). You can also see how light in color the resin turned after setting. Untinted resin normally turns white after setting, so it would be the same as if a little bit of dark brown color was added to a big bit of white color. The result would be a light brown.



Wait about 20-30 minutes for the resin to completely set before opening the mold. Undo the rubber bands and carefully work the mold apart. You don't want to just pull it open because it may break the casting, depending on what it is. A simple shape like a Moai will be much easier to de-mold than a human figure. Flex the side of the silicone that is holding the casting to help loosen it. After the piece is carefully removed from the mold, trim away the vents and flashing around the figure with an X-Acto knife.

I hope this has been helpful. I'm looking forward to seeing the results of anyone who posts them. Try it!











 
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Paipo
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Joined: Jun 22, 2006
Posts: 1886
From: Aotearoa / NZ
Posted: 2007-01-13 12:11 pm   Permalink

I wish this thread had been around a few months ago! I searched high and low on TC for info on casting to no avail.

A couple of questions - I've noticed that whenever I use the mold release, it forms a glaze on the mold when it dries, and the dye seems to form little blotches where this occurs, so I get patchy colour on my casts, and they also come out quite shiny, which I don't like. Maybe it's the wrong sort of mold release?

Does the talc not stick or get mixed into the resin? The only reason I haven't tried it is I'm afraid of having white dust stuck on the show side of my casting.

Anyway, thanks for adding another definitive post to the TC knowledge base - I'm sure this thread will be of immense use to future efforts.
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Bowana
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Joined: Nov 10, 2006
Posts: 1170
From: La Mesa, CA
Posted: 2007-01-14 7:06 pm   Permalink

Hey Paipo-

I use Krylon Silicone Spray when a release is needed. I've never had a problem with it causing the dye to blotch. It will however, put a slight gloss on your first few castings. Most of the molds I work with don't need any release. I only use it if I find that the flashing is sticking. What are you using as a release? Have you tried casting without it? Maybe you don't even need it. And what kind or resin are you pouring?

I've never seen any evidence of talc leaving a white dust appearance on anything I've cast.
I don't know what happens to it, but it's never been visible. It must mix into the resin to some degree. Try a test casting on one of your pieces. Let me know what happens!


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Paipo
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Joined: Jun 22, 2006
Posts: 1886
From: Aotearoa / NZ
Posted: 2007-01-14 7:17 pm   Permalink

OK, I'll try the talc for sure...I think the mold release I'm using is the one you are meant to use for two part silicon molds (so the silicon doesn't stick to itself) - I asked for mold release when I ordered my supplies and that's what I ended up with. So, it's probably wrong for what I'm using it for. It does help with air bubbles, but it sounds like the powder does a much better job. I'm using alumilite regular for casting. The castings do come out looking nice with no mold release, but with air bubbles where the detailing is very fine.
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VanTiki
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Joined: Nov 25, 2005
Posts: 1032
From: Hawaii
Posted: 2007-01-15 11:11 am   Permalink

This thread is fantastic!

I did a TON of molding and casting when I was working in LA - and I second all of the advice given above. I have always used foam core for making small molds - and it was the material of choice in the FX shop I worked at. The key I learned to make it easy is to use one strip of foam core that is scored only half way through 3 times to aid in folding it into a square. Tough to describe - mayhap this photo will explain better:



Talcum powder is great stuff for breaking the surface tension while casting - and I have found that drawing a cut line on the foam core inside the mold before pouring the silicone can help when cutting open complicated molds.

Finally - the "roto-cast" method rules if you don't have a vacuum chamber! I would pour the resin, cap the pour hole, and GENTLY rotate the mold until the resin has set. I'd get a great surface every time - you just have to be sure to do it gently - and make sure the pour hole is plugged well! I had urethane pour down my arms and all over my watch on a sad occasion or two!
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Paipo
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Joined: Jun 22, 2006
Posts: 1886
From: Aotearoa / NZ
Posted: 2007-01-15 12:56 pm   Permalink

What brand of silicon is that? Mine's pink.... and what are you using to hold the foamcore to the base...hot glue? Any recommendations on materials would be good, as it's terribly expensive here so I want to make sure I'm getting the best results for my hard-earned money.
I can also see I'm going to have to try some bolder stuff now I've got all this good info. Thanks!

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[ This Message was edited by: Paipo 2007-01-16 16:23 ]


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VanTiki
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Joined: Nov 25, 2005
Posts: 1032
From: Hawaii
Posted: 2007-01-15 5:04 pm   Permalink

Quote:

On 2007-01-15 12:56, Paipo wrote:
What brand of silicon is that? Mine's pink.... and what are you using to hold the foamcore to the base...hot glue?



Hey there - I use hot glue to stick the foam core to the base (which was discarded pergo floor shorts in this case - they make great little work tables!). The silicone in the photo is Silicones Incorporated GI 1000 - fabulous stuff that is also fabulously expensive. Lasts a long time, tho. They have several formulas depending on your application. I always freak out when I have to order silicone! I did just use some clear stuff lately that was not too pricey and held up really well.



I'll have to crawl around in the studio for the manufacturer's label... You can check out my "how to cast wax parts" section of my geocaching site here:

http://www.geotiki.com/geotiki/studio.html

Casting is always an adventure!
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Bowana
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Joined: Nov 10, 2006
Posts: 1170
From: La Mesa, CA
Posted: 2007-01-15 9:08 pm   Permalink

GI-1000 is my personal fav too. I've been using it for a good 14 years now. VanTiki speaks the truth that it's expensive though! The green silicone I used here is Rhodersil V-2025 made by Rhodia. It was available to me so I tried it. It's cheaper, but not as flexible as GI-1000. Plus, I was having some difficulty with the flashing sticking to the mold which never happened with GI-1000. Yes, I should be a sales rep for Silicones Incorporated.


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pdrake
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Joined: Jan 13, 2006
Posts: 1767
From: las vegas
Posted: 2007-01-16 3:23 pm   Permalink

mold making and casting videos . . .

http://www.freemansupply.com/moldmaking.htm

a little thing i found on the web while searching for supplies. some good info and pictures are always nice.


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