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The Mold ---------------------------------------------- -Making the mold is quite easy. It involves a two part combantion of a base(rubber) and a catalyst, (activator) mixed 10:1 (base:catalyst) then poured into, and over the original.
-The RTV rubber should set 24hrs. before you separate the original from the rubber mold.
Once the mold is made, there are a number of things you can cast with. I will explain this step further in part two.
--The photo show the original(lower left) and the replicas.
The cost is in the mold. The RTV rubber costs about $30.US per quart. Once the molds are done the replicas are only pennies each.
-------------------- Richard Bustamante Signs in the Pines www.signsinthepines.com Posts: 781 | From: Nevada City, California | Registered: Nov 1998
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i shouldnt have read this.....now ill be wanting to mold stuff...here goes some more wased money on one of my little trips! be real good if i made something to SELL..but i always end up making a bunch of useless crap to have laying around......thanks for the photos though there great
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I've seen cast sculptures....eagles, bears and the like...mostly in cigar stores, that are cast with crushed pecan shells and resin. The result appears to be real wood, dark mahogany color. I have some ideas what I'd like to do with this, but have never found a source for materials. Anybody have an answer?
Golden West MFG Inc. Cedar Ridge, CA 95924 USA 530-272-1133 FAX 530-272-1070
--I'm having so much fun; I feel like a little kid with a new toy. My Idea is to produce post caps (finials)(sp) for sign posts. I'v been researching what types of casting materials to use, and came up with "R-1 Fast Cast"; which is a general purpose, rigid, urethane casting resin.
--If you have any questions, I'll do my best to answer them.
-------------------- Richard Bustamante Signs in the Pines www.signsinthepines.com Posts: 781 | From: Nevada City, California | Registered: Nov 1998
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This is how to estimate the amount of RTV Silicone Rubber needed. Measure the mold cavity (length x width x height in inches) to get the total cubic inches. Subtract the size of the pattern. Example: The plywood case is 1.75" thick x 12" long x 14" wide = 294 cubic inches. The pattern is 1" thick x 10" long x 12"side = 124 cubic inches. The difference is = 174 cubic inches. The rubber weighs about .038 lbs. per cubic inch, so take the 174 x .038 = 6.6 lbs. of catalyzed rubber.
See sketch. Mount the pattern on a plywood base. Do this on a flat table. Use silicone adhesive, dispensed from a tube, around the perimeter to prevent any RTV from going in between the pattern and plywood. Wipe off any excess adhesive. Now screw the plywood sides to the plywood base to enclose the pattern.
-------------------- Richard Bustamante Signs in the Pines www.signsinthepines.com Posts: 781 | From: Nevada City, California | Registered: Nov 1998
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Mold Making can be a great addition to your sign buisness.I am a moldmaker by trade I have been making and casting Resin for over 15 years now and I dont know how I would live without using it. The posibilities are endless. It is one reason I got in to the sign buisness. I use to do Model Tanks and Airplanes and some sculpture.. Golden west is a great supplier and I use them pretty much exclusivly now. To Make real good mold you do need to make a small investment in a good GAST Vacuum pump and make a good Chamber so you can de-gas the rubber(Remove all the air) My Chambers are made out of 12 and larger 1/2 walled PVC sewer pipe and that is capped on one side and a rubbe seal on the other that seals the plex when you turn it on.. I could go on and on. If people are intrested I would be happy to write a small article on it for you... I love resin as much as signs.
I'm just getting ready to jump in with both feet on this kind of mold and casting stuff.........Thanks Richard.....and yes to more how to do it's.......
The more the better..........!!
Also.....Here's a really good book for starters
"The Prop Builder's Molding & Casting Handbook" Thurston James
You can get it from....... Lindsay Publications Inc. PO Box 538 Bradley, IL. 60915 815-935-5353
Lindsay has all kinds of really neat old time books ..... Their catalog is worth gettin'........
......cj
-------------------- CJ Allan CJs Engraving 982 English Dr. Hazel, KY 42049
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Richard Sorry if I stepped on toes this was your thread not Mine.. I just get a little over excited when there is a subject around that I actually know something about
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>>William Please, give us more. This thread is not a ****ing match, and I welcome any imput. I was hoping that someone like you would respond, and further educate us.
>>CJ It's a fargin blast. I'm molding the dog, a door knocker, a brass seal, an antique tile, and any thing I can get my hands on.
Questions: ------------------------------------------------ -How do I make a two piece mold? "I want to cast 3D objects."
-Is there any way to get the RTV rubber to set faster than 24 hours?
-What other types of casting materials can be used with rubber molds? "At the moment, I'm using "R-1" fast cast resin."
-Will vibration work for air bubbles during pour time? (RTV)
-Is R-1 resin paint receptive?
"Thats all for now. I don't want to scare you away?"
-------------------- Richard Bustamante Signs in the Pines www.signsinthepines.com Posts: 781 | From: Nevada City, California | Registered: Nov 1998
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Ill try to answer these the best I can do without photos.. I will put together a small Ebook and make it available for download in pdf format.. It might take me a week or so to put it all together. The simplest way to make a 2 peice mold is to make a mold box then pour rubber over the part then cut it in half with a mold knife.... If it as large part I will lay the part down and build a clay dam around it so only half the part is exposd along my parting line.(If it is a delicate part or very valuable I will first wrap it in one layer of saran wrap the build my clay parting section the slit the wrap and peel it back over the clay.) The I mix my rubber with a additive called Thi-Vex. This makes the rubber brushable. I will apply the rubber in a few coats of about 1/8th each coat so I end up with a 3/8th thick mold... Then I will Mix plater of paris with fiberglass additive for strenth and apply that over the rubber at about 1 inch or so.. Then flip it over and do again on the other side.. Make sure you use a parting agent of vaseline reduced with mineral spirts and brush onto the rubber so the rubber won't bond to itself..Or if you dont mind getting paint on part your molding I will just use Rattle can.. There are commercial available stuff to called Parafilm and others but these run around 12 to 15 dollars a can.. Thats a quick overveiw. Here is a usfull link. http://www.smooth-on.com/howtomakemolds.htm
You can get an accelerator for the rubber that will cause the rubber to set up in 1 hour but it takes some getting use to as your working time is cut down from 45 mins to 5 mins most of the time you cant get the air out that quick and it makes a poor mold for longivety standpoint...
If you are using an RTV mold you can cast just about any type of material you want in it including low temp metals. All that happens is you have mold breakdown faster depending on material.
I personaly have had very lttle luck with with vibration with the rubber due to its viscosity But for the resin it works very well except for the smallest pinholes or parts what i do then is I vacuume the resin in the mold or preasurize it at about 60psi in preasure pot.(Dont use cheap Preasure cookers...BOOM)
Resin is very paint receptive as long as you wash the part before use.. The Mold extracts a Silicone film on the part just wash it in mild soap and water or alcohol. I like using one shot as a base coat or if I am distressing it or weathering it I will usa a latex as a base then use oils on top.. That way Im not disolving the paint underneath...
ONE more good tip for resin and any other sign or HDU.. If you have a chip or crack use superglue and baking soda. Fill the chip with the baking soda the put a drop of glue on it. You will see a small puff of smoke and whalla instant patch.. Better then bondo or any filler I have ever used..Then just sand to match.. You think Im nuts but try it.
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And One shamelss Self plug..... I will be releasing a line of resin 3d sign ornaments sometime this summer as time permits. Some of the items will be rope designs that can be bent and glued to shape and the standard floral and scrolls.Im still designing them as we speak and molding them. All are computer cut replicas, pulled from original old world architecture or scanned with a 3d scanner. And Custom designs are available.
[ May 04, 2003, 11:42 PM: Message edited by: William DeBekker ]
-------------------- Richard Bustamante Signs in the Pines www.signsinthepines.com Posts: 781 | From: Nevada City, California | Registered: Nov 1998
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Wow! Luv it. Can you make a cast of anything? Beer or wine bottles? Little cute stautes? How about plastic flowers? Can you do fruit? Just wondering.
-------------------- Signs by Alicia Jennings (Mudflap Girl) Tacoma, WA Since 1987 Have Lipstick, will travel. Posts: 3967 | From: Tacoma, WA. U.S.A. | Registered: Dec 1999
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Richard,,, oooops... Well lets keep in contact so we dont do the same things.. Great Minds do think alike.. Or just confused minds .. Not sure which.. Alicia, Yes you can cast just about anything. I actually casted a dried rose for a client once.. One thing though.. If something is real delicate dont expect it to survive the molding process so if your really in love with the item enjoy the original... I cast alot of antique Christmas ornaments for a company but they know the old thin glass will not survive the demolding process.. Talk about getting it right the first time. They told me once how much they paid for an original and I was nervous as heck casting a $300 christmans tree ornament knowing I was going to destroy it so I told them I dont want to know anymore.
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