DIY Cement Skulls for Halloween

Intro: DIY Cement Skulls for Halloween

I thought I loved Halloween but my kiddo LOVES Halloween. With that being said I thought we needed some additional long-lasting, albeit cheap, decorations. I don't mean cheap in a way that it will die after the season I made them. If you know me, that is not part of my values.

So let's get to...cementing?

STEP 1: Video of My Process

Check out this video of how I Planned and Made these cement skulls.

STEP 2: Grab Some Cheap Skulls

I saw these at my local dollar store and picked up a couple. I bought two to start out with in case one experienced some sort of deleterious effect.

After working through this project, I may wind up buying more before the season is over or some other similar thing like a pumpkin head.

STEP 3: Tape, Cut, Pour, and Set

First thing to do to prep your skull is to tape over any holes so they don't leak. These are likely from the factory when they blew these things up.

Next, cut a hole to fill with cement. I used the cap of my cooking spray to trace an outline and then cut the hole out of both. Spray in the insides with something that will help release the cement when it dries. I used cooking spray. I heard it may discolor the front but we will deal with that later.

After that you can fill with your cement or concrete of choice...but how will you know how much to use? Good question.

STEP 4: Calculate the Mix

Warning: Math..!!

If you don't care to know the "why" behind this, just know I used 375 mL of water with 9.5 pounds of Sakrete for filling 2 skulls. Different brands of mix may cause your numbers to skew a little, for example, later I made two more using a fresh bag of Quikrete High Strength, and it came out to be 9.5 pounds of mix for 300 mL of water.

If you do want to know how I came up with my measurements, here you go:

With the hole cut out of a skull, I filled it with water and measured it out (pic 1). I got really close to 1 liter (pic 2) so that is what I went with. Now, I know 1 skull will hold about a liter.

The bag of concrete mix says one 60 pound bag will fill a 0.45 cubic foot slab (pic 3). Looking at (pic 4) shows that after some unit conversion, 0.45 cubic feet is ~12.75 liters of volume.

This is important since this bag calls for a 1:25 ratio of water to the concrete mix (pic 5).

I used that ratio to find out that 2 skulls will require ~9.5 pounds of mix (pic 6) and 375 mL of water (pic 7).

Looking in the previous step's pictures, after filling, I didn't have that much mix left over which was fine. I don't mind going over in the measurement, but more importantly, I didn't want to be too shy and have to re-mix after my first pour. That may risk some poor adhesion or other odd discoloration.

Whew, okay let's get back to it.

STEP 5: Remove From Shell

I let one of my skulls cure for 4 days in a [sort of] temperature controlled garage. . . and the jaw fell of...(pic 1).

I let the other one go for 3 additional days in the sun/heat and this is was waaaay better! (Later when I made two more skulls using the same cut up mold, they were fully cured with 2 half days in the sun!)

But we need to get this thing out to show you.

My plan was to try and slice three separate sections to aid in "peeling" the plastic from the cement. I decided on a "Y" formation and started at the chin (pic 2) and worked my way up to the hole I removed to fill in the previous step (Pic 3 & 4). After, I moved out from the top of the hole going toward the forehead area (pic 5 & 6).

Peel like an banana and hope for smooth release (pic 7 & 8).

I taped the cuts back together with duct tape and plan to reuse for future pours. You can never have too many skulls, am I right?!

Alternatively, you can take the back side out completely if you didn't want a [somewhat] full skull shape.

STEP 6: Paint and Finish

Pic 1 shows the better of the two. Pic 2 for comparison. The better skull is straight from the mold and was still slightly "damp" on the forehead / nose bridge. Don't let that discoloration discourage you :)

Let the skulls finish drying out for a day or at least overnight. Mine were still a little "powdery," but that may be due to the expiration date on the Sakrete bag? IDK but I have had that bag stashed away for >1 year. . .(I had way better adhesion with the new bag of Quikrete HS).

To start the painting process, I sprayed them with some white primer and allowed that to cure according to the instructions . You can stop here if that is what you're going for. No problems there since it looks really nice.

To give them a little more age, I did a 50:50 mix of acrylic black paint to water (pic 3-4). I did this to weather my plastic container (Junk Heap) robot Instructable if you want to know more about that process. Basically, just slather it on (pic 5), give it a few seconds to seep into the divots/low spots, especially the joints, eyes (pic 9), nose, and teeth. After, just wipe away with a lint free cloth (pic 6-7). Repeat until you are satisfied (pic 10 - 11).

You can also add some decomposition or other highlights by using more than just black for weathering. For now, this was good for me. If you plan on keeping them inside then you can stop here. If you want to place them outdoors, you will want to apply a sealer coat or two.

After the paint dried, I sprayed it all over, bottoms and back included, with two coats of polyurethane (pic 12-13) and allowed it to dry. Then you can put them all on display for the Trick or Treaters (pic 14), although full disclosure, this was more for me and my kid, lol.

I hope you like this Instructable and for a few bucks, you can make a whole heap of skulls!!

Catch you on the next one.

Comments

[jimicos]

I made similar ones last year, but with refractory cement. I didn't paint them. The fire and ash add their own color. The one on the left has been in the fire pit. The refractory cement is pricey, but worth it.

[Dankozi713]

Whoa those look really good!!

[jimicos]

Thanks. I like them. I have no artistic ability, so I couldn't ask for more. I only wish I had a mold that could produce hollow skulls. It'd be awesome to have flames coming through the mouth and eye sockets. Not sure how hardy they'd be, though.

[Dankozi713]

That would be really cool!

[snowf7]

Check out the skulls made by MadeByBarb. Hers are done in cement and look like what you are describing. I just went to the top of this article to the search area and used "cement skulls" as the search. Good luck.

[wannabemadsci]

The skulls look great.
I was planning on doing something similar but wanted mine to be able to go in fire so I was looking into refractory cement.

A couple of questions:
Do you know if the mold release is definitely required?
Did you vibrate or otherwise shake the molds to get any bubbles/voids out?
Thanks for sharing your cool project.

[Dankozi713]

Thanks for checking out my project!
For the mold release, I’m not sure if it’s absolutely necessary when working with these dollar store (I assume HDPE) skulls. HDPE doesn’t react with most anything. I haven’t tried not using cooking spray but let me know if you try it without and it works just fine.
Also, the second batch of skull i made, I didn’t vibrate my other batches and they look very similar to the first. All I did after the pour was smack it with the giant paint stirrer and some bubbles still floated up. However I used a lot leas water and my mix was pretty chunky comparatively.

Hope that helps and good luck!