pouring clear resin

[Meghan]

I am wanting to pour clear resin, or have someone do it for me, that is about 1 1/2 inches to 2 inches thick. I also want it strong enough to walk across and not scratch up so easily. Oh, they are also 18" x 18". Does anyone have any info on how to go about it? I have tried test pieces, but they have either pulled away from the sides or have rippled at the top. Do I need to heat up the resin? Any information or help would be wonderful. Thanks!

[fritchie]

I am wanting to pour clear resin, or have someone do it for me, that is about 1 1/2 inches to 2 inches thick. I also want it strong enough to walk across and not scratch up so easily. Oh, they are also 18" x 18". Does anyone have any info on how to go about it? I have tried test pieces, but they have either pulled away from the sides or have rippled at the top. Do I need to heat up the resin? Any information or help would be wonderful. Thanks!

Meghan - I have worked with resins some, but never anything like this, and I quit a half-dozen years ago because of either allergies (to some) or very noxious fumes (with others).

From what I have read about resins, you probably want to cast or cure this material not at a fast rate (i. e., hot), but slowly, with as little catalyst (the minor component) as possible. Also, I suspect you will have trouble finding a resin that will not scratch easily. Most are relatively soft, though I believe there might be materials you can spray on after finishing to improve scruff resistance.

Also, there are at least three resins to consider - epoxy, polyurethane, and polyacetate. As a chemist, I’m probably opening myself to severe criticism, because I should know more about composition, but it’s been close to ten years since I used these materials, and I’m no longer sure about details. Some, I used only once or twice.

I believe polyacetate generates the greatest amount of heat during curing, and it is the heat that probably causes warping. I remember from reading about these materials many years ago, that casts of 1 inch of greater thickness were prone to both cracks and internal bubbles, from the heat.

We do have people here who work more regularly with resins, so hopefully you will get better answers. I’m just trying to start the ball rolling.

[sculptor]

Hi Mehgan:

Bruce Beasley succeeded in casting large clear resins in the late 60s----He convinced DuPont to provide the material and created an autoclave to control pressure and heat(i believe he controlled bubbles with pressure)
see his sculpture "Apolymon (http://www.svam.org/Exhibits/Bruce_Beasley/Beasley_Final_Html/Apolymon_01.html)"

I have never tried a thick clear casting, but if I were to try, I'd start with Bruce and work forward

Let us know if you succeed and how you did it.

cool?
rod(sculptor (http://sculpture.alturl.com))

ps, as/re the casting, Bruce said, in part, In the late 1960’s I began to have dreams of transparent sculpture. I was fascinated by the idea of sculpture that you could see into and through. Sculpture where you saw the front and backside at the same time. What would be the esthetic problems of a transparent medium?
Research into glass and plastics quickly revealed that both glass and polyester resin (the traditional casting resin sold in hobby shops) are not sufficiently transparent at the thickness I wanted to cast. Further research led me to the conclusion that only polymethyl methacrylate, the acrylic plastic better known by the trade names Lucite and Plexiglas possessed the absolute transparency that I wanted.

Acrylic is one of the oldest plastics and in some ways it is still one of the most remarkable because of its outdoor durability and exceptional transparency. With these characteristics acrylic was the perfect material for the sculpture I wanted to cast, with one drawback. No one, including the manufacturers Rohm & Haas or Dupont or the military, had succeeded in casting thick sections without having it crack and fill with massive amounts of bubbles.

Casting acrylic is just the opposite of casting bronze. Instead of starting with a solid material and using heat to make it liquid, you begin with a liquid and use heat to turn it solid. The problems are twofold. The first problem is that acrylic shrinks significantly when it polymerizes (polymerization is the term for turning from the liquid to the solid state). The shrinkage not only distorts the shape, but it causes massive voids in the center of the casting. This happens because the outside of the casting polymerizes first and as the outside hardens and shrinks it pulls material from the center, thereby causing shrink voids.

These shrink voids appear to be bubbles, but they are actually small voids that have a vacuum in them. The second problem is that the polymerization or hardening itself is highly exothermic, meaning it gives off a great deal of heat. This causes a runaway reaction where the heat given off by the initial stages of polymerizing causes too many other molecules to polymerize too fast and the heat generated is enough to boil or even set on fire the acrylic that is still liquid.

I experimented for most of a year and was able to get to the point where I could cast acrylic up to six inches thick. This was encouraging but was far from the thickness needed for the sculptures I wanted to make. However, this size of casting allowed me to see enough to know that transparency had rich and exciting esthetic possibilities.

Just at this time when I had learned to cast moderately sized acrylic sculptures, I was chosen to compete for the first public artwork for the State of California. I was a young sculptor only twenty eight years old and this was a great honor and an important opportunity for a young artist. The state competition created a huge dilemma for me because I had been selected to compete in the competition based on my previous work in cast metal. My heart was in the ideas I had for transparency, but I did not know if I could learn to cast acrylic in really large sizes. I screwed up my courage, or you might say that I was foolhardy, and I entered and won the competition. I entered a model in cast acrylic not knowing know to cast the large sculpture that I would have to make and that I had confidently told the jury that I knew how to do.

With a lot of added motivation, I continued to do experiments in the direction that I had been pursuing, but I made little or no further progress in being able to cast thicker. It was as though the material was telling me that DuPont was right and that acrylic simply could not be cast in massive thickness. I did not know what direction to pursue next and I began to fear that I had been foolishly over-confidant and that I would be a failure at my first opportunity to do a large public sculpture.

I decided to approach the problem in a different way and to try to feel what happened to the material over the entire process. This allowed me to understand what was happening more completely than analyzing step by step what I thought were the critical elements. It sounds trite, but the understanding of what was happening, and therefore the solution, came to me in a flash. The next experiment produced a casting three times thicker than I had done previously, and I knew then that I could cast any thickness.

The casting of the big sculpture for the state capitol was successful. It is titled Apolymon and it is 15 feet wide, nine feet high and four feet thick.

Casting acrylic requires that the curing takes place under high pressure in a rather sophisticated and expensive device called an autoclave. It is basically a high-pressure oven. Since the entire casting has to cure inside, you need an autoclave with an interior space as large as your largest casting. The critical variables are catalyst, time, heat and pressure. The curing cycle increases as the casting gets thicker. Apolymon was in the autoclave for three weeks and during that time I did not know if the casting was successful or not. I timed the opening of the autoclave to correspond to the first moon landing – I wanted to benefit from any extra good luck there might be floating around.

best of wishes
r
pps-----I've seen pictures of Bruce's works in here, but can't remember the location------

[ABL83]

Contact ABL Stevens Resin & Glass - www.resin-supplies.co.uk, so so helpful, Lauren x x x

[ahirschman]

Polytek makes some clear casting resins (I can't get to their web page right now) but they would not be "scratch resistant."

When I saw the clear resins cast they first degassed by pulling a vacuum, and then cast right away under pressure. Degassing alone did not clear bubbles and pressure alone was able to clear "most" of the bubbles. The combination did the trick. You do not have much working time, so you will need help and lots of equipment.

Let us know what else you find out.

Ari.

[interferens]

I was looking at making big, clear blocks myself and remember finding a website for a supplier of epoxy resin that also provided instructions for how to use it to pour clear bar and table tops.

As I remember it, it said thicker applications could be done by pouring the epoxy in layers. I don't remember the name of the company, but maybe it's something you could hit google with.

[ahirschman]

Now that you bring up epoxy, you will have to pay attention (With any material) as to how much heat is generated in the curing process. Many of the regular epoxies will generate a lot of heat, and will burst into flames if poured too thick. The same can be said of many polyurethanes. As a rule, the slower the curing speed, the lower the temperature. I have poured epoxy that was only about 1 cm thick and it became so hot that it turned brown and started to boil. The easyflow clear from Polytek does not seem to generate a lot of heat and can be poured fairly thick, but will not be hard enough to walk on (I doubt any plastics will meet that requirement).

Ari.