how to cast big marble statue

[dilida]

I have some questions about casting two 7' statues of a man and a woman, separate, in bonded marble. If cast in pieces, because of the size, how does one go about putting the pieces together and working out the seams? And can large molds be slushed with resin? that doesn't seem very practical, but you couldn't hand lay-up inside a hollow 4' mold either, could you? Not crazy about this project, but told the boss I would look into it. I've searched this forum, but didn't find answers to these questions, and went to Smooth-on's website, but haven't contacted them yet.

thanks much
lisa

[Keropian]

Hello Lisa,

I don't get onto this forum that frequently, so you may already have your answers.

Check out my site on the sculpture process. I have some information about resins that may help you.

you can contact me directly if you have any more questions: http://www,keropiansculpture.com/bondbrz.html
http://www.keropiansculpture.com/process.html

Good Luck !

Mike

[ahirschman]

Hi Dilida, would you happen to have any pictures of the molds? How do they open? How do they fit together? How much do they weigh? How rigid are they?

Depending on how the mold is built, you may be able to paint or spread the resin on each piece of the mold. Then carefully join the mold pieces and add more resin to seal the joints or seams.

Slush casting is also possible, if the mold is built to withstand the abuse. You would need to use a resin that hardens fairly fast, or you will break your back. For 7' mold you will need a few people to agitate the mold. You can work on sections, adding some resin and rotating one area and building up the entire sculpture that way. That may be challenging. If you do it that way, you will have to get a nice layer built up, and then start to add reinforcing materials, such as chopped fiber glass with resin.

I join bonded bronze sculptures together all the time. I use one of my steel sculpting tools to match the texture and lines of the original pieces that I am joining.

One thing that you should be careful with is that for the outside layer of your sculpture (the one that is visible) you should maintain the exact ratios of your mixes so that the colors match exactly.

Another thing to watch out for is the type of release that you are using. If you are using silicone molds then you are not using a release and you will get the best results. If you are using a release and it gets in the areas to be joined you will have lots of trouble. If that happens you may be able to shave off a thin layer to expose a release free area. If the gap is big enough you can bring some material from the back area that has no release.

Send some pics and maybe I can give better advice.

Ari.

[dilida]

Keropian, thanks for the links, it looks like you applied the resin to the two halves, and then put them together, how do you get the resin to seal the seams in places you can't get too because the mold is closed? That's the one of my big questions.

Ari, thank you for your reply also. The molds haven't been made yet, I'll make them however is most appropriate for the project. So I'm guessing silicone, and maybe even resin mothermolds to keep them light. (I usually make hydracal/fiberglass mothermolds). We would have enough man-power to roll a complete mold around, but it just sounds scary, because what if you didn't get the resin completly covering every where? Applying the resin and then putting the molds together sounds safer to me. But how do you apply the resin to the seams if the molds are closed? Slushing the seams? If there is flashing do you grind or sand it off? And what if there is a gap instead of flashing? Can you just apply a small amount of resin and smooth it in? Same thing for air bubbles ,if any?

I don't have pictures of the statues, there are two, a man and a woman, but I have seen a picture. They are a white marble that were carved in the 1920's I believe. Kind of a neat story, they are E.W. Marland and his wife Lydie. He was an early Oklahoman oilman, who lead a very wild life, true to the wildcat days. He imported rock from Italy I think and had a Europian style mansion built in the wild west.. He married his adopted daughter after his first wife died, and these statues are of he and she. He made and lost his fortune twice, after he died, Lydie lived a lonely and strange existance in the carriage house of the estate. She had the two statues buried for a long time, and they have some damage, I guess we would repair that before we make the molds. The mansion is now a museum, and a donar has given them some money in the hopes of recreating the two statues in a material that is suitable to be installed outdoors. I personnaly like the damaged ones, they tell a far greater story than two replicas out of a cheaper material, but hey, it's thier money. The originals are on display inside the mansion and I would travel there to make the molds, so I'm thrilled about that part, and just getting to handle them would be cool. Daunting, but cool.

Thanks for resonding, it doesn't sound quite so intimidating, just scary now.
lisa

[ahirschman]

Hi Dilida, I thought I would give you some more pointers/ideas. First, a disclaimer: I do not work on large sculptures like the ones you are talking about,but I do create tall (almost 6') narrow bonded bronze sculptures that should have some similar issues.

I hope some of these are helpful. If nothing else, maybe these items will make you think of things that you had not thought about, and will make the final process easier.

Mold Material: If you can use silicone, go for it. You may consider a tin catalyzed silicone, as it has less inhibition problems. The mold will not last as long, but you should be able to use it for a couple of years. A very troublesome problem when working with sculptures that you cast in pieces and then join (Even if joining inside the mold itself) is that the mold release gets between parts, and keeps them from joining. When I cast my long pole bodies I end up getting thin layers that peel away because the first cast pulls away from the mold wall, and a second layer of bonded bronze flows between the initial cast and the mold. The second layer is prevented from bonding to the first layer because of the mold release. Patching and joining pieces is much harder for the same reasons. If you can't use silicone, the project is still possible, but you will have a little more work and you will have to be a bit more careful.

Sculpture Design: You have to think ahead how you are going to "cast" the sculpture and how you are going to provide strength. Many of the resins are very strong, and may not need much support. On the other hand, I like to provide support to any sculpture made of resin. I have used stainless steel rods, galvanized, mild steel, and of course, fiber glass. If you can pull it off, I would suggest using fiberglass whenever possible. That way, you will not have long term problems with the different coefficient of expansion (Cracks) and fiberglass will be easy to apply. Since you will apply the fiberglass to the inside, you can be fairly sloppy, and still gain a lot of strength.
Once you have two parts reinforced, you have to think of an easy way of joining them. For example, you may build up a respectable layer of bonded marble on each part of a two part arm mold. Then you reinforce the two parts, leaving some room near the edge to allow more bonded marble to flow in a slush casting directed only at the seam area. This works very well with bonded bronzes. The seam should allow bonded marble to flow in, and also should allow your reinforcement to be joined. Hopefully in one operation.
If you are not using mold release patching defects will be easy (But time consuming).
You may want to find out if you can use a dense expanding resin (Two parts that foam to produce a light but very stiff open cell hard foam). I would consult with the manufacturer of the resin you will be using. If you can avoid having to manually reinforce your sculpture you will save a ton of time, and effort.
If you find out that you can use a rigid casting foam for reinforcement, then your sculpture will be very easy (But... time consuming) to make.
When I do a simple bonded bronze (two to 6 pieces joined) I hand layer the bonded bronze directly to the mold, and I get very close to the edge of the mold. I can always trim the sculpture when I demold and I can always patch missing resin when I demold. I then (If I have enough room) join the two parts of the mold, and add some resin which I slush around the seam. I may add a few more slush layers to build up the bonded bronze thick enough to withstand some damage without revealing the backing resin.

Some of my parts are very thin, and I have little room between my stainless reinforcement and the mold, so I layer the bonded bronze, and then add the reinforcement while the bonded bronze is still liquid. It is a mix of hand layering and squash casting. It causes me all sorts of headaches, but I have no choice. You may have problems like these for narrow parts, like fingers. Fingers may just have to have a good skeleton to keep them from breaking off in the long run.

The main issue if you build the sculpture this way will be thinking ahead how the major parts will attach. (arms to torso...) I am certain that you will need some form of reinforcement at those points. Perhaps the torso will have a stainless tube, and the arm a stainless rod that can fit into the tube (With enough play to allow proper alignment while the joining resin hardens).

OK, enough here.

Mold Design: The mold design should take into consideration your reinforcement and building method. If you are hand layering your bonded marble then you want to give yourself easy pieces to layer and join. You want to make the pieces fit easily into one another...
If you are going to use expanding rigid foam as the core of the sculpture then you have to build your mother mold to withstand the expansion pressures during cure. These may be high on a large sculpture, so you will need lots of reinforcing ribs and lots of screws on the seams. I doubt that this will be a problem for you.

Random Thoughts:
Many resins stick well to themselves for a limited amount of time. This may be from a few hours to a day. Something to think about when making a large sculpture.
Exothermic resins (Most of them?) get harder to use in larger batches because the heat released makes a larger batch cure faster. Find the right balance - a compromise between speed and quantity. For some of the resins I use I can never use more than 800 grams of bronze in one pouring, and that would be for a very wide open mold where I can spread the bonded bronze resin very quickly. I have thrown out a few kilos of bronze that cured before I could use them. The best thing is to have someone constantly mixing the resin while you apply it to the mold.
After you apply the bonded marble you may want to keep on adding straight resin to a certain thickness to provide structural integrity. Many of the resins I use are very strong, and a 1/2" thick part would be very hard to break.
Resins are plastics, and may deform over time. That is why you may still need something to fill the inside of your sculpture for added rigidity.
I mentioned this before, but it is worth mentioning again. If you want your patches, and layers to match seamlessly, then make sure you weigh every mix to the same ratios of resin and additive (marble powder...)


OK, I hope that a few of these items will be of use, or will make you think of something useful for this project.

Keep us informed so we can all learn.

Ari.

[dilida]

Ari, Thank you so much! This information will be very helpful. I can follow directions from manufacturers, but hearing from experienced artists gives me confidence. So far there are no time contraints on this project, so I plan on a few practice runs with smaller pieces, so I hope to sculpt some similar forms and practice on them. Expensive I guess, but I'll feel better. You answered a lot of my questions, and gave me enough to know what sort of questions to ask the resin people. I can start to see in my mind what might be involved here.

Thank you again,
lisa

[ahirschman]

Good evening Dilida, I have a little more info for you. I had to purchase some resins today, so I asked about this sculpture.

The rep, a very knowledgeable person, told me that something like this would probably be cast in a rotocaster. I told him about the size and possible complexity, and suggested that the sculpture be broken into more reasonable sized pieces and then assembled afterwards. He thought that would be a good idea. Of course, if you can cast it in one shot then that will make your life sooooo easy.

I buy my resins from Polytek. They have one resin that is made for rotocasting - easyflow 120. You would have to build the outside wall thickness to a good 1/2" if you are to have enough strength. If you are not sure, go thicker, but that depends on your budget. Afterwards you would fill the parts with an expanding hard foam to add rigidity. You could use the marble on the first 1/8 to 1/4" and then keep on backing up the marble mixture with pure resin to get enough strength.

I have used easyflow 60 and easyflow clear, and I get very good results with both. You can use something like 1512 which is extremely strong. you may also have to add something to protect the resins from the sun rays.

Good luck.

Ari.

[dilida]

Thank you Ari! I'll look into roto casting. I've used a polytek resin before, but it was on a very small piece, and with bronze powder, so I know a tiny bit about it. It set up as I was pouring it into the mold, so I know to be wary of that! It was nice of you to discuss this with some one, thanks. If I can remember, I'll try to get a picture.

lisa

[ahirschman]

Thanks. I have used many of their resins and can help you with them. I think Smoothon and Polytek used to be one company and then split up. They probably have similar products, and so do other companies (My guess).

One has to really watch the work time with many resins. Also, if they are exothermic (Give off heat) then the more you mix the more heat that is produced and the faster the cure rate. You get used to the time constraints and they stop being much of a problem. There are resins made with longer working times, but even those are not long. 5 minutes may seem short, but if you are ready it is more than enough time. The resins I use have about a 2 minute work time, and I have gotten used to working with them.

Take care.

Ari.