24" * 18" * 24" Exo Terra with EPS foam stump prop. - Dendroboard

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Old 07-10-2019, 11:02 PM
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Default 24" * 18" * 24" Exo Terra with EPS foam stump prop.

Hello again, Dendroboard!

Recently, I had a chance to go through my parents' wooded property, about 5 acres of which is wooded and overgrown with undergrowth. I was going mostly for inspiration, trying to find a setting for a terrarium, or part of a terrarium.

I took a LOT of photographs of very nice things, but I became enamored with one photo:

It hadn't looked as impressive when I took the photograph. But when I looked back at the photographs I had taken later, I could see a very attractive stump with many grooves and recesses fit to grow plants in.

Obviously, a rotten stump fixed in the ground isn't the best option for a terrarium, but I had read recently about the process of artificially converting wood into driftwood, and thought I would give it a shot.

So, the next day I set out with a yardstick to ascertain the dimensions ... and I found that it was much larger than I had remembered. It was about 36" off of the ground, and about 24" wide and 24" deep. Nor could I just cut off part of the top and convert that to driftwood; the flared out base was what made it a stump, and made the spiky top parts that spread out seem more significant. And even if I cut it off, I would have to risk it undergoing the driftwood-conversion process, which may well not work on partially-rotted wood.

Instead, I decided to make a foam model of the stump. I had read and watched tutorials on how to do this, in more than one way. I had many times over the supplies to make a foam stump. So I took a bunch of photos, printed them for quick reference, and set off.

This is the agent that I will be working with to cover the surface of the foam prop once it is done. Drylok is no stranger to vivarists. Mostly I'll be using it to add texture to the EPS foam, because straight painting acrylics on top of it wouldn't make it look too stump-like. It is somewhat expensive, though.

These are the most important tools for the foam, and probably for the entire project. They come from Hot Wire Foam Factory, a business well known among model-makers. If you aren't familiar with these tools, they heat up a narrow metal wire by using a power station plugged into the wall. They serve variable purposes:

The hot knife is the first tool. Slices through things, good for making pits. It will be useful in creating the rot-holes in the stump.

The sculpting tool is the second one from the top. The taut wire is useful for eliminating mass and creating the general shape before fine-tuning.

The precision engraver is the third tool. It's useful for extremely fine details. As such, it doesn't heat up as much as the other tools, and can be put on very low heat in order to make precise marks.

The freehand router is the bottom-most tool. The wire can be bent into different shapes for different purposes. It is probably going to be the most important of the four hot wire tools for this project.

I stacked a few leftover EPS foam sheets for practice, in order to test the foam tools and color mixing Drylok:

It's a bit difficult to distinguish the contours because the foam is white, but these are practice sculpts. The freehand router was used to carve all of this. Like in the photo of the four docked tools earlier, the freehand router has three bulges, and each one is different. I can keep things from looking symmetrical by turning the tool upside down, then right-side up, and varying it in that manner continually during the sculpting process.

Mixing colors to correctly get what I want to be the base colour of the stump has been a struggle. At first, I did not know that I could use acrylic paints in Drylok, so that I just used the three different colors of concrete dye I had available. Those were charcoal, buff, and brown.

The lighter, tan / beige / cream / yellow color you see is nearest to what I want to cover the foam with first, but it isn't quite there yet.

I will be making notes to myself as time goes on. This is another uninhabited terrarium, so whatever chemical problems are created by melting EPS foam will not be a concern.

As always, I welcome any cautions or suggestions from anyone.


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Old 07-11-2019, 02:53 PM
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Default Re: 24" * 18" * 24" Exo Terra with EPS foam stump prop.

Excited to see how this thread turns out, I've always admired these custom wood build threads. I've used drylok before but I'm not good enough with colors to get something that looks nice right away (have to wait till plants grow over for things to start looking good...), nor am I good enough at sculpting the foam to get the shape I want (though the freehand router probably makes things a lot simpler?).
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Old 07-11-2019, 07:44 PM
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Default Re: 24" * 18" * 24" Exo Terra with EPS foam stump prop.


Yes indeed, the freehand router makes work a lot easier. All of that uncolored example piece (and more work since then) was done with the router, and all done with the exact same wire pattern on the router. Since then that practice block has been made to look like similarly all the way around.

I don't think that I am going to need the sanding disc / sanding drum on a rotary tool that the guide I borrowed from mentions using. (I also hate the mess it creates.) I definitely won't need a knife; I experimented cutting through EPS foam and pink foam and the sculpting tool does the job so much faster it's ridiculous.

I don't know whether or not melted EPS can leech through a good sealant, so I can't recommend these tools for anyone trying to create a vivarium prop with animals living near it in the tank. But for all other purposes, hot wire tools are a godsend.

As far as colouring Drylok goes:

It took 3 gallons & 1 quart of Drylok experimenting, involving various acrylics and concrete dyes, to finally arrive at a color as near to the base colour I want the foam to be painted with as can reasonably be made. (Without turning the whole mixture into acrylic paint.)

I did the mixing next to my previous terrarium, with its 6500K lights, as those are most similar to the quality of lights that are going to be used in the terrarium containing this model. There is a noticeable difference in the shade or tone of colored Drylok between being under this light and being under a warm, 3100K light.
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Old 07-16-2019, 11:04 PM
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Default Re: 24" * 18" * 24" Exo Terra with EPS foam stump prop.

I've done some work on it, and a lot of testing.

This is an example of the materials I use to figure out the texture:

^The rotting wood is taken from bits of the stump, and the magnifying glass helps me get a better view of the texture.

Some texture attempts, covered with drylok:

^I haven't really been able to reproduce the patterns on the wood, though I have had a lot of study material to work with. Many, many photographs of the stump, about ten minutes' worth of video footage closeups, and a couple pieces of the wood itself

I have done some work on it, though, after the foam glue came in:

^Still has a ways to go. I'm not even sure if this structure will be what I go with, even though I've practiced plenty on yet another foam structure. I'm not wild about the way it's looking so far. It's really hard to get the spire-like shape of the real stump, even with very efficient hot wire tools.
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Old Today, 07:05 PM
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Default Re: 24" * 18" * 24" Exo Terra with EPS foam stump prop.

Some updates:

^Underside of the eggcrate platform

^Top of the tank, with glass cut and hole drilled in it, plus a screen panel sized to fit the remainder.

The glass was not quite wide enough to comfortably rest on the sills, so I used epoxy clay to make something for the glass to rest upon.

^Photo of part of the cracks that may spell the end of this tank. I don't know yet.

^Front view of the finished form of the stump. Since then I've covered it in one layer of Drylok, but I don't have a photo of that yet.

^Back view. Because the back will seldom ever be seen, I did not put much detailing on it, and I used it for additional testing of the texture / color.

^A view of the prop on the eggcrate platform inside the tank. I plan to surround the platform with turface in order to disguise it, but I'm not sure yet.

All in all, I don't know about the direction of this project. The prop doesn't seem to have the same striking lines and points of the source. It will take a lot of careful paint work to achieve the coloration of the real stump, and I don't know if it will look the way I want it to look by the end of all the work.

EDIT: Oh, and:

^Two holes in the top surface for drainage. There will be soil and plants in these pits.

Last edited by Kinstrome; Today at 07:12 PM.
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drylok, foam, hot wire tools, stump

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