I’ve made a decision about what I want to do to cover the base area of my concrete porch. After going through several different ideas last week, I finally decided to go back to mine Original We have an original idea and cover the base area with Austin stone to match the stone part of our house.
I wanted to do that from the beginning. When I built the floating wood porch over the concrete porch years ago, my original vision was to carry the Austin stone that covers half of the front of our house onto the porch. Austin stone is a white/light limestone that is ubiquitous in Texas, and it is called Austin stone here in Texas because it is mined in the Austin and Texas Hill Country area.
The problem I ran into at the time was that I couldn’t find an Austin stone that matched the stone on our house. I didn’t care about matching the color since ours is painted. Unfortunately, our stone was already painted when we bought the house, so my choice was to either have it sandblasted or repaint it the color I wanted. I chose the second option because it was faster and much cheaper. And to be honest, I don’t really like the color of the natural Austin stone anyway. As I said, this stone is ubiquitous in this area and has been for decades, so it’s nothing special in my humble opinion. I much prefer the light gray of our house to having the siding portion match the yellow-beige color of a natural Austin stone.
But the problem I ran into is that Austin stone in the late 40’s and early 50’s was cut very differently than modern Austin stone. Here is a more modern building with a facade made of Austin stone (with the natural color of Austin stone), and you can see that the stones are cut so that they are quite flat on the fronts.
Here’s a closer look at what it looks like. Nowadays all Austin stone is cut this way.
And here is a look at the stone in front of our house. Just by the way the stone on the front is cut and carved, you can immediately tell whether it is modern or whether it was built around mid-century. Back then they carved the stone so that the center of the front of each stone stood out much more. There are not many stones in our house that have a flat surface.
So when I tried to find the right Austin stone (real or fake) to match our house, it was virtually impossible. I found some May worked, but they were generally pretty expensive and I didn’t want to pay that much for something that didn’t fit exactly. So I finally gave up on that idea and tried to find other ways to cover the baseboard.
Well, after trying a few other ideas and then thinking about a few others, I’m back to the Austin stone idea. No, I haven’t found a source for matching Austin stone. Instead, this time I decided to make my own. Here is the process I decided on: (1) I make my own silicone molds (i.e. textured mats) using our house’s stone as a mold for the silicone molds. (2) I use these textured silicone mats in simple concrete molds that I build to fit the size of each mold (or textured mat) I make. (3) I create my own stone facade pieces from an aerated concrete mix so that the stone facade is lightweight and can be attached to the front of the concrete base area and (4) prime and paint the stone to match the rest of the house.
I have no idea if this will actually work, but I’ll have fun trying it out! I’ve already made four silicone molds (one failed and three successful) and I think I need a total of six usable molds for my porch. This process was actually very simple, so I want to show you how I did it.
How to Make Easy DIY Silicone Molds (Two Ingredients):
This is not my original idea. I saw this process on YouTube (I shared this video with you in last week’s post) and it made it look so easy. So I decided to try it out and see if it would work for my project.
To make your own silicone molds, you will need two ingredients – 100% all-purpose silicone paste and cornstarch. I used a glass bowl and poured a whole packet of cornstarch into the bowl. You can use the cheapest cornstarch you can find. Unfortunately, this brand from Bob’s Red Mill was the only brand available at the store I happened to go to, and at about $3 a package, it costs about twice the price of cheaper cornstarch. But the cheap stuff works perfectly.
And then I used my caulk gun and squeezed two whole containers of silicone caulk right into the middle of the cornstarch.
And then I put on some gloves and started mixing the caulk into the cornstarch. I tried my best not to touch the caulk directly because the stuff is really sticky. Basically, I folded the cornstarch onto the caulk, moved around the bowl, and folded the cornstarch onto the caulk all the way around the bowl until the caulk lost most of its stickiness. I stopped when the mixture of caulk and cornstarch formed a ball that felt like playdough.
And then I selected the stone I wanted to use to form the first silicone mold and pressed the silicone and cornstarch ball onto the front of the stone. I really had no idea what I was doing on this first one, so this was my test.
I gave it about three hours to dry. While it was drying, I used a sieve to remove any leftover caulk from the remaining cornstarch so I could reuse the leftover cornstarch for the next mold.
Removing the silicone from the stone was a challenge and when I pulled it off it removed some of the paint from the stone. (You can see what color the stone was painted when we bought the house. Blah. I definitely didn’t want an entire house painted that color.)
This is what the silicone mold (or textured mat) looked like when I removed it. I doubt this will actually be usable as concrete will likely stick to those rough spots. But this test gave me insight into what I needed to do for the next one.
I was rummaging through my cupboards to see what I could use as a mold remover and found this small bottle of olive oil that had been sitting in my cupboard for far too long to use for cooking.
So next time, before I pressed the silicone onto the stone, I covered the middle area of the stone with a very thin layer of olive oil. I simply used my gloved fingers. I didn’t apply it all the way to the edges because I needed the silicone to hold something in place, and if the whole thing was covered in olive oil it wouldn’t have anything to hold onto. But I really only needed a mold release agent for the most heavily textured areas, i.e. the middle part of each stone.
And then I took off my gloves (I didn’t want to mix olive oil into the silicone) and coated my hands with cornstarch to press the silicone onto the stone. I had about 15 minutes of work time with each silicone/cornstarch ball.
That worked perfectly. Again, I let it dry completely for about three hours and when I pulled it off the stone it looked great! No color comes off the stone. Therefore, using a mold release agent is key to achieving a great result with the textured mat.
After my second test was successfully completed, I ran two more at the same time. Since the base area of my porch is quite short, I wanted to make a mold for a few shorter and smaller stones. I chose this one…
And this is what it looked like with silicone pressed on…
And then I decided on this little one.
Here’s the one with the silicone…
Both turned out great too. The oil used as a mold release agent is key. But again, I only applied the oil to the most textured middle parts of the stone so that the silicone would stick to the outer areas where there was no oil.
It took a lot of trial and error and of course a lot of waiting (about three hours for each one to dry before removing), but I think this idea will work. Right now I have three usable forms and one failed. I want to have a total of six usable shapes before moving on to the next step. I need to cut these shapes and then build some sides around them to have something to pour concrete into (I’ll mix aerated concrete) to give me my complete shape for each stone. So stay tuned to see if I can actually pull this off! Right now I’m about 75% confident that I can do this.
