Making Easy Lava Cracks in the Ground for Halloween

Cracks in the earth, under Vecna from Stranger Things yard.

After seeing the last season’s episodes of Stranger Things, I knew I wanted to recreate Vecna, the lava cracks in the earth, Billy, and Max. I watched a few other creative tutorials, but as usual, I decided to make mine a little differently. The differences in my version of lava cracks vs. others I found online:

1) I couldn’t find any tutorials for long, narrow, lava trails, busting out of the earth, (as in Stranger Things). Most were wider, and seemed to be missing the black edge, that should be seen, from where dirt is displaced.

2) The tutorials out there seemed to use more spray foam, or unnecessary items, to get the effect needed.

3) Digging into the ground was not an option. So, here’s how I managed to make those lava cracks:

Supplies Needed for 18ft. of Lava Cracks:

  • 2 packages of 200 count indoor/outdoor orange light strings (each length 41.5′)
  • Black pool noodles OR Black pipe insulation foam (18 ft)
  • Plastic Sheeting (Black or Clear) 2 – 9ft strips, about 2.5ft wide
  • 2 cans of Big Gap Filler Spray Expandable Foam, and a pair of plastic or rubber gloves
  • 2 cans of Economy Spray Paint (1 black, 1 red)
  • Plastic 2 liter bottles (about 12 per 18ft strip)
  • Plastic 16 oz. bottles (about 6 or 8 per 18ft. strip)
  • *Plastic 1-liter bottles can also be used (see Choosing Bottle Sizes/Cutting in the heading below, for more info)
  • Clear Box Tape
  • A Heat Gun with low/high settings
  • Heat Resistant Gloves
  • *Optional items: A Hot Glue Gun/sticks, clear or thin black irrigation tubing, mini Demodog flower heads, sticks, etc.

Directions: Cut your 2, 9 foot strips of plastic. Don’t go narrower than my suggested width. With the technique I use, you’ll need that extra width for heating the plastic to the black foam noodles.

Once the plastic is cut, lay it out on the ground in the shape you’d like. It could be whatever shape you want, you’ll just need to make more cuts in foam later, to follow the shape. I went more simple and made a giant “V” for Vecna. But shh…I want to see if anyone in the neighborhood gets that.

If you’re working with pool noodles, you’ll have to cut them in half, length-wise (see below image). If working with pipe insulation, usually there’s already a slice down one side, but you’ll need to cut it completely through(making 2 pieces). Follow the preset cut in the insulation tubing, for an even cut. Once the foam is cut, lay them on the edges of your plastic, in the shape/position of your choice. But leave enough plastic hanging past, to either wrap a bit around the noodle, or you can adhere it directly flat with your plastic edge. Either works, and in places I did not have enough plastic to wrap, I used the clear box tape to keep the noodle in place, while heating/melding it with the plastic.

To meld the foam noodles with plastic, you take the Heat Gun(preferably wearing heat proof gloves) and heat the plastic wrapped about an inch around the noodle, OR flip the plastic (bottom side up), and with the noodle taped, heat the plastic until it adheres to the foam. I tried it both on high and low settings. If you’re used to using a heat gun, the high is fine for quick work. If you’re unfamiliar with using a heat gun, try the low setting before trying it high, so you can get a feel for how it melts plastic and foam. Once all the foam pieces adhere well to the plastic, you can move on to the bottles.

Cut noodles or foam insulation tubing lengthwise
Foam noodles and pipe insulation is melted to edges of plastic strip.

Choosing Bottle Sizes/Cutting Them

When you consider which size bottles to use, remember the bigger the bottle, the higher the lava mound will be. This is helpful when not wanting to spend a lot of money and time, adding extra foam. Two liters will give the highest mound, but mixing them up, can make a more natural-looking mound. My “V” of lava was made with 2-liters and 16 oz. bottles.

As shown below, the left 2-liter bottle has the bottle wrap removed. Take off as much of the bottle wraps as possible. It’s ok if there’s residual wrap pieces here and there. Some bottle brands have a pesky glued label end. Don’t work too hard to get that off. It won’t be seen, when you’re done following directions.

Take your plastic bottles, and cut the top and bottoms off (see image below, for blue cut lines).*If you plan on making Demodog Blooming Heads, don’t forget to save those bottoms of the 2-liter bottles.

From left to right: 2-liter, 1-liter, and a 16oz plastic bottle with cut lines.

Once the tops/bottoms are cut off the bottles, make a horizontal cut from top to bottom of each bottle. *If you have bottles with a patch of glue/wrap residue, make your cut on that side.

Attaching the Lights/Bottles to the Plastic

Before placing any lights into the bottles, please check that the lights work – even new ones out of the box. Unwind a string of lights. Plan out your strategy of which end of light plug you’ll need available for your power source, and plan your bottle strategy(lay out all bottles on plastic to ensure they fit within the plastic length made).

You’ll be grouping lights (about 15-20 bulbs) and taping them to the inside of the plastic bottles – on the opposite side of horizontal cut. Then setting the horizontal sliced side down, onto the plastic(having the taped lights side showing on top). Use clear box tape to secure bottles to plastic. Be mindful of the length of lights you have. Using my length of lights, I calculated about 20-22 lights per foot, but used a few less for the space between bottle openings. Remember, I used 41 feet of lights for just 9 feet of lava.

After all the lights have been secured into the bottles, and placed on the plastic, recheck the lights to ensure they are working. Once that foam goes on, it will be quite difficult to remove or switch out the lights.

Adding Foam

Now that you’ve rechecked lights, you’re ready to add the spray foam. Put on those plastic gloves, and if you have clothes you care about – switch to some work clothes. Anyone that has worked with spray foam knows it is the stickiest, and sometimes a nightmare, to get off your clothes, skin, or whatever. So if you’re a newbie, read the next heading. If not, skip on to the next directions.

Words of Wisdom For the Inexperienced Spray Foam User

For those who are using spray foam for the first time, you’ll be surprised of a few things:

1) You’ll actually need to shake that can a full minute, for the foam to mix well, and get the most out of it.

2) You won’t think you’ll need the gloves, and that you’ll be careful. Wear them.

3) The foam comes out faster than you expected, so easy on that trigger.

4) You’ll want to spray more than you should (give the stream of foam a few minutes, and it will expand, more than you expect).

5) Your first thought of washing off the foam, (from your skin or clothes), with soap and water, is NOT the answer. Water actually cures the foam, making it tougher to get off. Instead, immediately wipe as much off as possible, and use acetone or nail polish remover with acetone, to get it off skin. Clothes might be a bit trickier. Acetone can take color off, or degrade material enough to make a hole.

Spraying the Foam on Top of the Bottles

You will only need 1 can of spray foam per 9 foot of lava. Spray foam trails randomly over the bottles/plastic, paying attention to bottle to bottle connections, and in between the space of the bottles/black foam tubes. Do not try to cover the bottles completely, and it’s okay if you run a little over onto the black tubing (which represent broken earth). But try to stay mainly on the bottles, and spaces within the plastic bottom. Repeat for the other 9 ft. section.

Once you’ve emptied the foam cans onto the lava area, Push in the optional tubing, Demodog heads, sticks, or whatever you want protruding into the lava. It will stick, as long as the foam is still wet. You can also add items after the foam dries, attaching pieces with a hot glue gun.

Final Touches

After the foam has dried, and possibly added items protruding the foam, randomly spray black and red paint, across foam area. Pay attention to the obvious areas that show light bulbs, clearly. Do not spray heavily, because you want those lights shining through, but not looking like a string of Christmas lights.

Once dry, and when it gets dark enough, turn on the lights. See the magic you’ve created.

If you have any questions on any of my tutorials, please shoot me an email, or put it in the comments. Thanks!

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