Concrete Letterpress Sign

Introduction: Concrete Letterpress Sign

About: I am a multimedia maker and STEAM educator living in Los Angeles. There are few things more satisfying to me than acquiring and exploring a new skillset, so you'll find a wide variety of materials in my projec…

I got a set of wood letterpress blocks on a whim a while ago, and the Shapecrete Build Night at CRASH Space gave me the idea to use them to make a cement sign. I discovered while making my Concrete PotHead that a thermoplastic like Instamorph works well for making molds, so I used that to make impressions of the letter blocks.

Another option is to make individual molds for each letter and make concrete letterpress blocks. This has its own challenges, like getting the wood blocks back out without damaging the molds, but it is pretty neat.

I've included a video of me making this project in high speed on my new YouTube channel Barb Makes Things.

Step 1: Materials

  • Shapecrete
    • Bucket/Container for mixing
    • Cups/Water bottles
    • Plastic sheet
    • Stick for mixing (if using bucket)
  • Letterpress blocks (I used these from Tim Holtz)
  • Instamorph for molds
    • Pot for hot water
    • Hotplate/stove
    • Tongs
    • Needle-nosed pliers
  • Acrylic paint (both darker and lighter than the concrete shade, I used black and silver metallic)

Step 2: Making the Mold

The letterpress blocks I used are meant for decoration, not function, which you can tell as they aren't backwards. This is perfect for my purposes, as I'm not looking to make functional cement letterpress blocks either.

Heat up the thermoplastic in hot water and press into a thick pancake, then press the desired letters into the plastic, leaving a little extra around the edges. Once you have all of your letter impressions, take the excess plastic and bend it up to make walls for your mold.

Step 3: Mix and Cast

These don't take a whole lot of concrete, so only mix a little bit unless you want a big cup-shaped doorstop (which is cool too). It's best to mix it closer to the casting consistency than the clay consistency, to make sure you get all of those details in the molds, and to minimize bubbles. I mixed my concrete in a gatorade bottle, using a halved water bottle for both measuring cup and funnel, then shook it vigorously to mix. This worked pretty well and wasn't nearly as messy as using a bucket.

WARNING: Don't pour or wash any of this stuff down the drain, or it will harden in the pipes.

Scoop or pour your mix into the molds, poking, shaking, and tapping them as you go to make sure the mix gets all the way down. A couple air bubbles can turn "I Love Kate" into "I Love Kale."

After you've finished, tap the whole thing against the table a few times for good measure. You'll get more bubbles coming up, which is good. Better out than in. Cover with plastic and leave for a day or two.

Step 4: Removing the Mold

The nice thing about doing this with a thermoplastic like Instamorph is that, once it's had a day or two to dry, you can drop it into a hot pot of water, mold and all, and wait for the mold to soften up, which makes it much easier to remove without damaging the cement letters.

If you make the sign pretty thin, however, be aware that it likes to crack while removing it from the mold, and putting it in hot water apparently aids in that process. Oh well. You can always glue it back together.

Bits of cement may stay on the plastic, limiting your reuse of it, but I like to clear off as much as I can.

Step 5: Paint

You might like the letters as they are, but you can add a little more contrast by painting a bit. I've used acrylic paint to emphasize the dips around the letters and the raised sections. A little color can be fun too.

Step 6: Fin

Display your creation wherever you like, or even turn it into a graphic for your website. :)

Hope you enjoyed, and make sure to subscribe to my YouTube channel, Barb Makes Things, for videos of more projects.

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    6 years ago

    What a great project. I'm thinking of making one of these for my nameplate in front of my condo.

    On the Shapecrete site they note that one can use pigment to color the 'crete. But they don't make it clear whether they supply pigment. There is generic pigment for 'crete, at least there was when my Dad remodeled our back yard in 1948.

    There are letterpress blocks for part of the alphabet available on Amazon:

    The product got trashed in the Amazon reviews because people didn't realize when they ordered that the non-reversed letters would come out reversed when they used them as stamps. Hahahaha,


    Reply 6 years ago

    haha, come on, people. Tim Holtz makes really neat products, but they're *decorative* rather than functional.

    you might want to make it thicker than I did to hopefully avoid the cracks, or maybe cut the mold off rather than heat it off. (share pictures if you can!)

    ShapeCrete Mix
    ShapeCrete Mix

    Reply 6 years ago

    Any concrete pigment or stain will work with ShapeCrete. We're working on a line of colors that will be out in the next few months. In the meantime most good hardware stores will have pigment from Sakrete or Quickrete, and you can also buy really nice colors online from Cheng Concrete or Davis Colors.

    ShapeCrete Mix
    ShapeCrete Mix

    6 years ago

    Another great project, I'm going to have to play around with Instamorph. I'm surprised that it cracked. How thick is it? We don't usually have issues with projects cracking, especially at 1/2 or 3/4" thick, but we also don't submerge them in hot water either. If the piece was cold, I could see that causing problems.


    Reply 6 years ago

    it's about 1/2" thick, which is thin enough to be less than rock hard. but it was definitely the hot water that did it, it was fine before that. the cracks were enough that I could have easily pulled it apart, but not so bad that it just crumbled. it's possible that a thicker sign wouldn't have that problem. I wound up glueing it all to a piece of plywood slightly smaller than the sign to give it support.

    I still like the result, and the cracks sort of give it more character.


    6 years ago

    Using instamorph is genius! I'll need to do something like this sometime!