An Artistic Adventure

One gift of thoughtfulness led Steve and I to make a unique plaque for some special friends. These friends had mentioned offhand that they wanted a sign for their mantel that read: “A mighty fortress is our God,” so we jumped at the chance to make it for them. First, we had to select an affordable medium that enabled letters to be cut easily. Should the plaque be made of metal? Wood? Stone? Cutting letters out of metal seemed too difficult, and we figured that wood cut with a scroll saw or carved by hand wouldn’t look very good, given our limited abilities. We considered sandblasting stone overlain with a stencil, but didn’t have the right tools. Finally, with the help of the artists at Aardvark Clay in Las Vegas, we decided to make a Texas-style, faux limestone plaque from plaster of Paris. We had never poured or carved plaster of Paris before. The rest of this post will show how we did it and what we learned. Here we go!

The plaque needed to be 1” thick and 3” tall (to fit the mantel’s limited height). We first decided on Copperplate Condensed font, an imposing font which matched the limestone-like material and conveyed the “fortress” theme. Printing out the letters, we decided the plaque needed to be about 42” long, which allowed some space on either side of the words to affix metal “Texas stars” for embellishment. Next, we built a mold for pouring the plaster of Paris. We used three 42”-long two-by-fours to make a trough, with scrap wood covering each end. It was very important to use screws for the assembly so the mold could be disassembled easily to remove the dried plaster later on.

We used cheap modeling clay (about $9 for a 25-pound block) to dam up the gaps in the wood and then line the entire trough about ¼” thick. The 3 ½”-wide two-by-four, lined with ¼”-thick clay made the resulting mold just about 3” wide, perfect for the required height of the plaque.

I made the mistake of lining the trough with clay during Sam’s naptime, then getting interrupted when he woke up and not returning to the project until the next day. When the clay dried (moisture was sucked out by the dry air and the dry wood), the clay cracked and crumbled away from the wood. We needed to find enough time to work with the clay and pour the plaster, all within a few hours. Thankfully, the workability of the clay could be extended as long as we kept moistening it, but we needed to do both steps in one stretch.

After lining the trough with clay again, we needed to texture the inside of the mold to look like limestone. This was the hardest step of the entire project, and we weren’t entirely satisfied with the results. We used two limestone rocks (brought with us from Texas) to make imprints in the clay, but it was hard to get a random pattern with only a couple of unique flat surfaces. Thankfully, once the letters were carved later, the plaster would look more realistic.

We mixed the plaster using the following common instructions we found online: calculate the volume of plaster needed, put half that volume of water in a bucket, then sift plaster into the bucket until plaster is no longer immediately absorbed into the water. We let the plaster sit for a few minutes before stirring (being careful to not incorporate air bubbles when mixing). We coated the mold with dish soap to act as a release agent. Unfortunately, the thickness of the dish soap seemed to mask some of the detail in the clay mold.

After pouring the plaster, we let it set for about 3-4 hours before carefully unscrewing the wooden mold and peeling off the clay (of course, we were unable to salvage the mold).

Because we were worried about the strength of the plaque (we were worried about bending forces since the plaque was so long and thin), we considered reinforcing the plaster with landscape fabric we had on-hand. However, we were concerned that the fabric would sink to the bottom of the mold and show through the carved-out letters, so we omitted any reinforcement.

Next, we colored the plaster. Limestone gets an orange tint from naturally-occurring rust, so we made a “rust solution” from iron sulfate we had (iron sulfate, a fertilizer, is great for making homemade concrete acid stain), and drizzled the solution onto the plaster.

Carving the letters was surprisingly easy. From a printout, we traced the outlines of the letters with a thin, mechanical pencil onto the soft, still-drying plaster. The pencil’s thin tip made a narrow impression, yet made it easy to tell on the paper which outlines had already been traced.

After removing the paper, we used utensils of increasing diameter (first the mechanical pencil with lead retracted, then round-tip tweezers, then a nail head) to remove plaster from the inner boundaries of each letter. We used a nail tip to better define the tight corners of some letters. After carving, any remaining dust and rough spots were easily smoothed away with a fingertip. The plaster remained soft enough to work with easily for the three days’-worth of Sam’s naps it took to complete the carving step.

As a final step, we had to design a way to hang the plaque. At either end of the plaque, we drilled ½”-diameter holes then inserted ½” spacers through which to fasten screws. We then attached the Texas stars to the screw heads with magnets; this way, the stars can be removed to access the screws if needed.

We also had to figure out how to transport the plaque to Texas, ensuring it would survive being entrusted to the airline as checked baggage. We made a custom crate out of one-by-fours and inserted the plaque after wrapping it snugly in a towel. We were so relieved it survived the trip!

Here is a picture of the finished plaque: