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Sculpting/ Molding/ Casting Tutorial Thread « Thread Started on Jan 27, 2009, 4:40am »
With this thread I will try to impart onto those interested my methods for sculpting, molding and casting. I am not trying to give every little detail here- just a general ovrview of the process. I will use one of my dino sculpts as an example project.
First what I do when I am going to sculpt any animal whether it is modern or prehistoric is to do research to find any and all information i can regarding that animal. I use google image search and I go to my library to get books with photos. I try to find a good as near perfect side view of the animal to use as my starting point. I enlarge or scale it to the size required. Then I transfer the silhouette to either stiff cardboard or masonite and cut it out.. I make the arms, legs or whatever appendages separate from the main body, and then i hot glue it all together to make my armature. I also glue the cardboard pieces all together with a wire of some kind- usually either a cut up wire hanger or some floral wire. The wire helps to give the cardboard extra support, and also allows me to bend the armature around to put it in a pose and to hold that pose. I attach a length of wire coming out of the bottom of a foot, and this gets glued down to a wood scrap that I use for a base.The armature should be attached to some kind of base, so you won't have to hold or handle it as you sculpt.
Next I start to apply my clay to the cardboard armature. It sometimes helps if you apply a thin coating of shellac or thin layer of paint to the cardboard to help the clay stick to the cardboard. I use a plastilene clay- an oil based clay that never dries out- I use a brand called Roma, found at any good art supply store here in the U.S., which comes in various firmnesses rated by number- I generally use No.2 which is a medium firmness. The clay comes in blocks which I chop up into small pieces. I keep a nice supply of it in a plastic garbage can with a hole cut in the lid that I stick a hair drier through. The hair drier I run on low while I am sculpting, to keep the clay nice and warm, to keep it soft and pliable, saving me from having to knead the clay to make it malleable. I cut another hole to allow some of the heat to escape the garbage can, so the clay won't get too hot and melt. I apply a thin layer of clay over the whole armature, making sure to smear it hard onto the surface, making sure it is adhering properly to anchor further applications of clay.
Once the initial anchor layer of clay is complete, I start to add the clay in larger pieces, attaching them into the anchor layer, smearing these additions into the anchor layer , building up the bulk of the animal, roughing in the basic form. At this point I am just trying to get the rough form, and at the same time making sure it is attached well to the anchoring clay. This is important, as if you don't get a good attachment, you might have some clay falling off from the weight of the bulk clay mass as you build it up.I am not worrying yet about smoothing it out or starting to finish it. I try to keep moving all over, working everywhere at once- this helps to keep the pose fresh. Details will be added later once the roughing in is successful.
Once the clay is roughed in I start to try to 'see' the surface I want to get. I try to see where the low spots are and where the clay is too high in relation to this surface. I fill in with small pieces of clay where needed and scrape off little bits where needed til I start to see the surface tuning in. I don't start to add any final details yet, this is all about working the whole surface - not staying in one spot too long, moving around the piece, looking at it, seeing what needs what. Once the surface is smoothed out, and it looks good, I start to add details like wrinkles, scales, hair or whatever the animal requires. I make any tools that will help me to get details. Dinosaurs tend to have scales, so I make texture tools- I use balsa wood, making various size and shaped pieces that I sand to smooth rounded ends that I then push the tip of a pen or other implement to make various scale patterns in reverse- as the pen tip makes negative depressions in the wood. When these tools are pushed carefully into the clay they make positive scales on the surface of the clay, I dip the tool in water so the clay doesn't fill up the negative recessed scales in the balsa wood tool, and it keeps the texture crisper in the clay. I also have many metal plaster carving tools, wax carving tools and dental tools with different tips that help to shape and carve the clay(A firm called Sculpture House sells many of these such tools, or they can be found cheaper on ebay frequently). I find that metal tools are easier to keep clean and any tools can be dipped in water to keep clay drom sticking to them.If the amimal has fur or hair, I just draw this into the clay using a small sharp tool tip, usually startin at the head and working back towards the tail and down to the feet. This allows you to keep the fur looking like it is growing in a proper coat. Sort of like petting a cat- you don't want to go against the fur-lol.
Once the sculpt is detailed, I take some lacquer thinner and dip a soft but firm brush into it and brush the whole surface of the clay with the thinner.The thinner removes all the little burrs in the clay from dragging tools through it, and just generally ties the whole surface together- sort of like blending paint in a way. When this is done the sculpt is ready to mold. The lacquer thinner sort of melts the clay slightly so you wnat to do this sparingly and with a gentle touch, once you do this step it isn't a good idea to go back and work the surface any as the clay is softer now and any tool marks will be noticeable- I'm not saying you CAN'T go back and touch things up, but you have to be very aware of the difference in the clay surface, and you will have to rebrush the thinner again over any tough ups. Basically I try not to have to do anything else once I lacquer thinner the surface- this is a step done when totally satisfied with the details of the sculpt.
When I start to mold the piece- the first thing I do is I first get a board that is big enough to give me plenty of room to set up the molding forms around the sculpt. I use a 3/4 inch thick piece of plywood usually, as it is strong enough not to sag or warp as I make the mold- you want to keep it stable through the whole process. I set the sculpt on its side in the middle of the board, and prop it up to make it as fairly level as I can get it. I use a few hunks of clay under the sculpt to do this, always anchoring any clay to the board, a little shellac can also help the clay to grab the board-
Next I take clay and start to build up a foundation around the sculpt to hold the parting line shelf. The parting line is where the parts of the mold will separate at. It is best to study the sculpt before you even start this process, to find and plan out the best way to have the mold come apart. If it is going to be a flexible mold, as in this case, you can get away with having some undercuts, the mold will give so it isn't a big concern. If you are going to cast a rigid piece in a rigid mold, you usually have to have more pieces to your mold to avoid having your piece get trapped in the mold by undercuts. Basically you try to split the piece down the middle as much as possible to simplify the matter down to its root problem. This mold for the Rex will be a three piece mold- two main pieces splitting in half around the third piece which will be underneath between the arms and legs.So I build up to just below this line along the sculpt where the parting line will go for one of the side pieces of the mold-the third underneath piece will be poured last, into the cavity between the two side pieces once they are done-
Next I add the shelf that will make the parting line when the mold material is cast against it. I try my best to keep it right on this line, and to keep it clean and neat(nothing worse than a sloppy seam line) - going all around the sculpt-making sure there are no gaps between the shelf and the sculpt and making sure it is attached to the sculpt well without ruining the sculpt. A good tool is very important for this process.
Once the parting line shelf is complete, I add registration keys around the sculpt keeping as close to the actual sculpt as i can while still having room to get in to smooth the keys down to the clay surface of the shelf. It is important that there are no gaps anywhere between the keys and the surface of the shelf, don't want mold material getting underneath the keys. I make the keys by making slabs of clay and taking my official U.S. Army WWII mess kit knife(any sharp blade will do), and slicing through the slab of clay holing the knife at a 45 degree angle in one diraction and then making a pass the opposite direction. This gives me strips which in cross section have a flat top with the sides sloping away at 45 degree angles- the shape of a Roman arch keystone.
Next I set up a retaining wall around the sculpt, just outside the keys, leaving myself some room again to be able to get in to smooth the clay without wrecking the keys. I reinforce at the corners and the bottom with clay rolled out into long 'snakes', this helps to hold the walls all together to retain the weight of the silicone. and helps to ensure there are no gaps for the silicone to leak out of.
Now it is ready to mold- In this case it is all clay on the inside so there is no need for any release agent of any kind- If say the piece I was molding was made of plastic or some such material i would spray a release on it to make sure the silicone would come off of the piece I am molding.
Thats the end of todays class- I know some of it was a review of previously posted information, just thought it would be convenient to have it all in one spot here.. I will post the actual molding of the Rex for our next class. I hope that some have found it interesting - sorry for the epic length of this post.
"Boy, do I hate being right all the time!" - Ian Malcolm
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #6 on Jan 28, 2009, 12:45am »
NOt familiar with the term sticky used that way- I assume it means sticking with the thread - following it. Thanks for the encouragement, glad that someone finds it interesting. Hope it helps someone on a project.
I guess I am confused exactly what you are asking me here. The process is the same, no matter the size or the animal. I can understand though- it might help to see a few different situations to get a better idea of how it applies to different sculpts.
RIP SPUNKY June 26, 2009 - May 11, 2010 I still love you little spunk man!
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #10 on Jan 28, 2009, 3:59am »
I made this mold in a RTV silicone (RTV stands for room temerature vulcanization)which gives me a flexible mold. I get my silicone from a firm called Eager Polymers, here in Chicago. I am sure there are local suppliers near you. Eager's website is very helpful and they are more then ready to answer any and all questions about materials and methods if you call them, they are nice people. The silicone is a two part mixture. There is a thick white base componant that you add a thin blue liquid activator to to start the vulcanization process. It is reccomended that you measure out both parts with a triple beam scale - and they reccomend using a vaccuum chamber to get bubbles out of the silicone before you pour it into the mold form- but I say bullocks to all that. I just mix the two parts together without measuring, using the color of the mixture to judge by- quicker and less of a hassle- have been mixing silicone this way for years- never had any problems. I also don;t bother using a vaccuum to get out bubbles. I use a different system to get bubbles out which you will see- So I mix the two parts together and thoroughly mix them , scraping the sides of the cup I am mixing it in, scraping the bottom, scraping the silicone off of the stir stick a few times as I mix, until i get a nice even blue color with no white in it anywhere- IT IS READY TO POUR!
I pour it over the sculpt slowly, letting it rise up over the piece a bit, when there is a sufficient coating, without filling up the mold form all the way yet- I use a air nozzle hooked up to compressed air from a compressor to blow lightly over the surface of the sculpt through the silicone- I am pushing the silicone into all the little nooks and crannies of the sculpt with this process, getting rid of bubbles on the surface of the sculpt. This is the crucial thing here- to get any bubbles off of the sculpt surface.
This mold form needed to be leveled off before filling it the whole way- as the shape of the piece wasn't flat and the top of the mold form walls weren't parrelel to the plywood base the mold form is built upon so i propped it up to level it then filled it all the way up-
Now I just wait for the silicone to set up- I usually wait until the next day to start the next step, which is making the mother mold or casing that holds the flexible silicone to keep the shape it is in with the sculpt inside, this prevents the silicone from flexing when you cast the piece, which would give you a distorted cast. See? Working with silicone isn;t that hard and people like to make it a lot more complicated than it has to be, with all that measuring and evacuating with the vaccuum chamber and all that . I poured this side of the mold from start to finish including getting the material out of the bucket , mixing, pouring, blowing with air to get rid of bubbles in 15 minutes on my lunch break(I get a half hour lunch break), still having time to go out and have a cig before getting back to work. Next post I will show you how to make the casing that holds this side of the mold. Tune in next time when we will learn about polyester resin, fiberglass, and the joys of those materials-lol.
"Science is always discovering odd scraps of magical wisdom and making a tremendous fuss about its cleverness" - AC
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #12 on Jan 29, 2009, 4:05am »
So the silicone is set up the next day- first thing I do is to remove the clay walls without removing the clay parting line shelf- I clean up the shelf, smooth out any damage to the surface. I trim the edge of the silicone mold, putting a bevel on it, this helps in the making of the casing, eliminating the sharp corner so the fiberglass wrapps easier over the edge. I then take a round ended tool and swirl it in a circle to make recesses in the clay surface that will make registration keys. These keys are enough to hold the rigid fiberglass/resin casing in position. There will also be bolts holding the two halves of the casing together-
To make the casing I use a ployester resin reinforced with fiberglass. The system uses three components- the gelcoat resin, which is a thick resin, the consistancy of yogurt- the fiberglass mat which is actually glass strands bonded together into a cloth- and the laminating resin which is a thinner resin liquid that is used to soak the fiberglass to set it into a plastic material with glass fibers to give it its remarkable strength. The resins are two part systems, you add a catalyst to the resins to create heat that creates a chain reaction in the molecules that link up and make it harden, you can control the speed of the set time by how much catalyst you add to the resin- here is what the fiberglass looks like in the cloth form, it comes in large sheets or rolls and you cut it up to usable pieces-
You lay out the fiberglass pieces and use a brush to soak the fiberglass with the laminating resin which has been catalysed-once it is soaked through it can be applied to the piece-
So first I apply a generous layer of the gelcoat resin-catalysed and mixed thoroughly- over the whole silicone mold and the clay parting line shelf-
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #13 on Jan 29, 2009, 4:19am »
Then I apply the fiberglass soaked in laminating resin to the layer of gelcoat resin-
I trim off the excess once it has set enough to trim with a blade-
Then I flip it over once the fiberglass has setup. I take out the clay that had formed the foundation to hold up the parting line, and remove the parting line clay as well-
Now I have to clean up the sculpt- getting rid of any of the clay from the molding, and to touch up the sculpt before starting the second side of the mold.
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #15 on Jan 29, 2009, 4:47am »
Yes, there is always fixing up to do- unless the pattern is made from sculpey or something similar- a rigid pattern- I don't think its worth it though to sculpt in sculpey- plastilene is such a superior sculpting material for creating sculpts with life, and for details- sculpey just doesn't take details in the same way though others may disagree with me- The next part that was done was the second side- the bottom third piece was poured into the cavity between the two sides- I had to remove the wood base to do this as it was in the way to gain access to pour the third piece- I will post those steps as I find time as i have done so far up to this point.
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #17 on Jan 30, 2009, 1:29pm »
Yes the teeth survived fine- I used a sculpt epoxy to make the teeth so that they would hold up without getting smashed. I am also going to be able to reuse the teeth on other sculpts as well, like first of all the Tylosaur I am working on now-
Anyone who has a hard time with the fact that Aves are maniraptoran theropods must not have a firm understanding the biology of modern birds!
dinonikes Faunacasts subforum moderator member is offline
What would an alien culture surmise about humans if they only studied ten skeletons of humans?
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Re: Sculpting/ Molding/ Casting Tutorial Thread « Reply #19 on Jan 31, 2009, 3:35pm »
I thought I's post a few photos of finished molds- it is interesting to see how different each mold is- a direct result of the difference in each sculpture molded-
Here is the mold for the Mammoth model that you can see on my Classified 'Prehistoric Models' thread. It has the body and the spearate tusks in the same mold- I use brown resin to cast the body and white resin to cast the tusks. I will give a tutorial on casting in resin/fiberglass in the near future- basically it is similar to the method described in making the casing for the T-Rex mold- although there are tricks and details that are different.
This mold has s een a lot of use- many casts have been made out of it. Silicone holds up real well, and if stored properly can last many many years- notice that this mold has no registration keys- the odd shape of the mold is enough to hold the two halves in register to each other , and the bolts hold it together too..
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