Translucent rock formations

cckaiser2 · Jan 15, 2017

I'm in need of some assistance. I'm looking to create some backdrop scenery for prop display. Specifically looking to create fake rock walls. Here's a pic from a local aquarium that had translucent rocks with lights behind them - looked like ice. Any suggestions on how to create them?

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TazMan2000 · Jan 15, 2017

Crystal growing kits simulate a very realistic effect, but to make something large will take several kits, and may not be able to be joined together in order to create the look you desire.
Another idea would be to find realistic rock making kits from a miniature Rail Road store and use clear casting resin to create those rocks.

TazMan2000

cckaiser2 · Jan 15, 2017

These are huge. Each rock is probably 3 feet around. I could tell they were hollow and held together at the seams by some sort of caulk. I've researched making fake boulders but can only find concrete or spray foam options which I'm certain aren't translucent. I'm looking to create the cave from Hoth(or a loose representation of it). Probably just in the corner of a room in my house to display some SW items.

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cavx · Jan 15, 2017

Casting resin could work.
How many rocks do you need?

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cckaiser2 · Jan 15, 2017

I'm not sure - the room is 8' tall and I'd likely put them floor to ceiling in a corner - maybe attach a few to the ceiling.

I thought about doing some fiberglass boulders over styrofoam cores but can't figure out if clear resin and fiberglass would work for the ice look.

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Digital octane · Jan 15, 2017

I recall one of the recent tested videos the guys from weta workshop cast a rock face for the thunderbirds set. However I can't remember of the top of my head what medium they said they used ... may be worth a look. If I get some free time I'll pop back to YouTube and have a recap. I feel like saying fiberglass is going to be the most cost effective option but it would obviously require painting to achieve the desired look

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cavx · Jan 16, 2017

cckaiser2 said:
I'm not sure - the room is 8' tall and I'd likely put them floor to ceiling in a corner - maybe attach a few to the ceiling.

I thought about doing some fiberglass boulders over styrofoam cores but can't figure out if clear resin and fiberglass would work for the ice look.

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Fibre glass resin tends to be more yellow than clear. It would work though.

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division 6 · Jan 16, 2017

Perhaps you should ask at the aquarium about who made the display, then contact the company about how they did it.

There was a post on a Hoth display for conventions someone did using foam sheets that was well done, might want to look for it here on the forum.

JPH · Jan 16, 2017

Amazon had led strings that tolerate being embedded in resin. I used glow in the dark pigment around the LEDs so even when shut off, if exposed to sunlight they will glow some. But that is gonna be a lot of resin. Mix the resin ssllloooww to minimize bubbles.

GrenadeKing · Jan 16, 2017

If your making something bigger than a shoe box, use fiberglass and a translucent resin. It does exist. You might have to do a bit of searching but, someone is likely to have it. To get that melted effect, you'd just need some some high gloss cleat coat. Then you can light it up from behind with LEDs or whatever.

I guarantee that the aquarium did something similar. No way they spent hundreds of thousands making solid resin ice walls weighing hundreds of pounds each.

cavx · Jan 16, 2017

JPH said:
Mix the resin ssllloooww to minimize bubbles.

On a project that big, he should probably have a degassing chamber.

cckaiser2 · Jan 16, 2017

I'm certain they were resin of some sort. I wish I could have seen them in the light. The room was dark - only lit by the lights built into the rocks. When I tapped on them they were hollow. If I had to guess they were probably a milky white color and when lit from behind they were translucent in variations due to the varying thickness of the resin. They were design to be able to withstand kids climbing on them or bumping into them with feet or strollers.

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cavx · Jan 16, 2017

GrenadeKing said:
If your making something bigger than a shoe box, use fiberglass and a translucent resin. It does exist. You might have to do a bit of searching but, someone is likely to have it. To get that melted effect, you'd just need some some high gloss cleat coat. Then you can light it up from behind with LEDs or whatever.

I guarantee that the aquarium did something similar. No way they spent hundreds of thousands making solid resin ice walls weighing hundreds of pounds each.

I guess it depends on how much UV it gets exposed to as well. The resin I used in my last fibre glass project was a "wax finish" (meaning it feels waxy, not tacky like some polyesters can and do) and it is bluegreen as a gel, then, once you add the kicker and it starts to go off, it becomes clear.

I poured the excess on top of some wooden fence posts and it cured a whitish colour, but more cloudy then clear. Guess because it is thick. If it was thin with fibre, it might actually be translucent which would backlight.

cckaiser2 · Jan 16, 2017

cavx said:
I guess it depends on how much UV it gets exposed to as well. The resin I used in my last fibre glass project was a "wax finish" (meaning it feels waxy, not tacky like some polyesters can and do) and it is bluegreen as a gel, then, once you add the kicker and it starts to go off, it becomes clear.

I poured the excess on top of some wooden fence posts and it cured a whitish colour, but more cloudy then clear. Guess because it is thick. If it was thin with fibre, it might actually be translucent which would backlight.

That sounds like the right stuff - these were waxy feeling. Since these would be in a room - UV light would be minimal. Any thoughts on the process? If I build up a styrofoam base and cover with small pieces of fiberglass cloth - will that work? That's what I'd do with fake rocks but I'd end up painting those. I'm wondering if I can just do it without painting it. Maybe a clear coat as another post suggested.

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JPH · Jan 16, 2017

Um, resin only needs to be on the visible portion. Maybe an inch or two thick. If you want to make resin icebergs, still, only the outside needs to be coated. If you the internal structure is empty, except for some blue and white painted 2x4s, only you will know

lmgill · Jan 16, 2017

If I had to do this with minimal tools and budget, I'd carve Styrofoam into an approximate shape of the rock, cover it with tin foil, being careful to make sure seams where flat and slightly over lapping. With the "chrome" side up, as this will give the resin the desired effect. Tape the seams with a minimal amount of clear packing tape. Then use clear polyester resin and cover the foam/ foils base form in layers until the desired effect is achieved. (A light dusting of "Pam" food grade spray release may be required. A test of how the resin sticks to the foil should be done)
For fiberglass laminating, there are 3 different types of polyester. Gel coal, which cures with a harder surface and generally is opaque in color, laminating, which remains a bit tacky when it cures, so additional layers can be added, and the "waxy" resin is called finishing resin and this wax is added to give the final inside lamination a tack free surface.
There is also clear casting resin, which can be used for laminating. Polyester resin is an exothermic resin and cure is achieved by a chemical reaction that produces heat. Therefore, room temperature can have a dramatic effect in the curing. The more mass, larger amount of resin, the less MEKP catalyst is needed. If too much MEKP is added to a casting or a cup of left over laminating resin sits, it can produce enough heat to catch fire. Too much MEKP will also effect color, turning a blueish resin yellow or brown. Sometimes this is an effect designed into the resin to help indicate a cured material from uncured.

edit: The reason for covering the Styrofoam is, polyester resin will "eat" or dissolve polystyrene based materials.

cavx · Jan 16, 2017

cckaiser2 said:
That sounds like the right stuff - these were waxy feeling. Since these would be in a room - UV light would be minimal. Any thoughts on the process? If I build up a styrofoam base and cover with small pieces of fiberglass cloth - will that work? That's what I'd do with fake rocks but I'd end up painting those. I'm wondering if I can just do it without painting it. Maybe a clear coat as another post suggested.

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I saw the notification after mid-night last night.

If you use styrofoam, test a small bit with some resin because sometimes the glass resin eats the foam. Not that it will matter too much here. In fact that may even work in your favor as you will need to remove the foam later anyway. If any sticks, hit with acetone and it melt right off.

With fibre glass, the panel needs only be a few mm thick. This will depend on the weight of the matting used. The cheapest stuff is the chopped mat. The best matting is a woven material and it does not break up like the chopped mat. The chopped matting is easier to work into odd shapes, but the stuff is nasty, itchy and generally messy unless you are experienced in fibreglass. The woven matting costs a bit more, but so much less painful to work, especially on big sheet projects.

I would suggest watching a heap of YouTube videos on this first. You will see many differing opinions, but in the end, the strongest fibreglass is the one that has full saturation with the minimal amount of resin.

The way it works is that the resin dissolves the glass fibres in the matting when it sets, the fibres provide reinforcement. Over saturation leads to brittle parts. Under saturation will crack or leave glass exposed. None is desireable. On their own, both the matting and resin are not strong, but once combined correctly, they become very strong.

Fiberglassing is an art form for sure. Wear gloves and preparation is the key. You NEED your matting cut to size BEFORE you start any resin work. Only mix the amount of resin you can work. The stuff is exothermic, so in a colder climate, you need more kicker. Here where I live, where it reached 114F (the other day), mixing at 2% instead if 3% gives a slightly longer potlife.

The beauty of what you are doing here is that you can add lumps and bumps later. The glass will stick to itself well.

Good luck.

lmgill · Jan 16, 2017

cavx said:
I saw the notification after mid-night last night.

If you use styrofoam, test a small bit with some resin because sometimes the glass resin eats the foam. Not that it will matter too much here. In fact that may even work in your favor as you will need to remove the foam later anyway. If any sticks, hit with acetone and it melt right off.

Polyester resin will always melt polystyrene foam. Urethane foam it will not. Epoxy resin with not attack either foams.

cavx said:
With fibre glass, the panel needs only be a few mm thick. This will depend on the weight of the matting used. The cheapest stuff is the chopped mat. The best matting is a woven material and it does not break up like the chopped mat. The chopped matting is easier to work into odd shapes, but the stuff is nasty, itchy and generally messy unless you are experienced in fibreglass. The woven matting costs a bit more, but so much less painful to work, especially on big sheet projects.

Terms for these items in the glass industry is mat or cloth. "Chopped strand mat" is individual strands bonded with a sizing or glue. "Roving" is glass fiber in long continuous lengths that are fed into a chopper gun and sprayed into a mold. Woven material is Cloth. Cloth is available from very very fine, to over 1/8" thick. There are also many different weaves. (There are around 10 different types of glass used in these, but for this type of application the chemical composition of the glass in not important.)
Cloth is ultimately stronger and can be made to contour to most shapes, mat, is easier to use in oddly shaped molds, or where ultimate strength is not required.

cavx said:
I would suggest watching a heap of YouTube videos on this first. You will see many differing opinions, but in the end, the strongest fibreglass is the one that has full saturation with the minimal amount of resin.

The way it works is that the resin dissolves the glass fibres in the matting when it sets, the fibres provide reinforcement. Over saturation leads to brittle parts. Under saturation will crack or leave glass exposed. None is desireable. On their own, both the matting and resin are not strong, but once combined correctly, they become very strong.

I think you mean to say the resin dissolves the sizing or glue that holds the chopped mat fibers together. The resin does not dissolve the glass fibers. In a fiberglass composite, essentially, all of the strength comes from the glass, excess resin just makes the composite weak.
The property you are getting from the glass (Or carbon or Kevlar) is it's incredible tensile and compression strength. (It's resistance to pulling or compacting) The property you get from the resin is it's ability to glue the fibers together. Once glued together, the fibers cannot slide past each other, so the only way they can move or your finished composite can bend, is for the fibers to be compressed or stretched, the exact thing the fibers are best at resisting. So, the glass is the strength, the resin just controls how the forces of bending, act on the glass.
Think of it a bit like a full soda can and an empty one. The liquid is not "strong", but it cannot be compressed. The aluminum of the can is strong, but the very thin sheet used in a can, bends easily. But put the fluid in the can and you can stand 5 or 6 people on one can. Empty, it will just hold one person, if you don't move.

The GEcho · Jan 16, 2017

Silmar 249 (aka surfboard resin) is a clear polyester resin. It's blue in the can, mixes green when mixed with MEKP but cures clear. You can add surfacing wax tor spray it with PVA after it cures to remove the 'tackiness' . Both will result in the loss of tackiness, but you will need to spray the PVA off with a hose.

cavx · Jan 16, 2017

lmgill said:
Polyester resin will always melt polystyrene foam. Urethane foam it will not. Epoxy resin with not attack either foams.

Is the due to the heat or simply the chemical make up? Years ago, we made a fishing pontoon from the walls of an old cold room. I am sure we fiberglassed over the foam on that without issue.

I was told Epoxy is OK on foam but have not tried that.

Terms for these items in the glass industry is mat or cloth. "Chopped strand mat" is individual strands bonded with a sizing or glue. "Roving" is glass fiber in long continuous lengths that are fed into a chopper gun and sprayed into a mold. Woven material is Cloth. Cloth is available from very very fine, to over 1/8" thick. There are also many different weaves. (There are around 10 different types of glass used in these, but for this type of application the chemical composition of the glass in not important.)
Cloth is ultimately stronger and can be made to contour to most shapes, mat, is easier to use in oddly shaped molds, or where ultimate strength is not required.

Thank you for that detailed explanation. The process amazes me, though I have to admit, I am no expert. I do have a project that I am thinking will be best if fibreglass is used. Can you use polyurethane resins with fibreglass (say cloth) or does it have to be the specific polyester resin?

I think you mean to say the resin dissolves the sizing or glue that holds the chopped mat fibers together. The resin does not dissolve the glass fibers. In a fiberglass composite, essentially, all of the strength comes from the glass, excess resin just makes the composite weak.
The property you are getting from the glass (Or carbon or Kevlar) is it's incredible tensile and compression strength. (It's resistance to pulling or compacting) The property you get from the resin is it's ability to glue the fibers together. Once glued together, the fibers cannot slide past each other, so the only way they can move or your finished composite can bend, is for the fibers to be compressed or stretched, the exact thing the fibers are best at resisting. So, the glass is the strength, the resin just controls how the forces of bending, act on the glass.
Think of it a bit like a full soda can and an empty one. The liquid is not "strong", but it cannot be compressed. The aluminum of the can is strong, but the very thin sheet used in a can, bends easily. But put the fluid in the can and you can stand 5 or 6 people on one can. Empty, it will just hold one person, if you don't move.

I'm no expert on this, so yeah that is what I meant.

Translucent rock formations

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