As a bit of a departure from what I said in my post about only blogging when I have a complete project, this is kind of a halfway post. It’s still a finished thing (a wall) but it’s also part of a larger thing (a house).
Since making my ruined farmhouse I have wanted make some different buildings, brick rather than flagstone as at some point I’d like to build up a complete city worth of buildings (a lofty goal!). Rather than tediously carve each brick, on every building, this needs a modular approach (as tested with the farmhouse) and my own molds.
Once again enthusiasm worked faster than the camera, so I forgot to take images of the prep work. Text shall have to suffice.
The first step was to create the wall “master”. To do this I created a framework out of Lego bricks that fitted the dimensions I wanted. I had a rough guide to the size I needed from the farmhouse project, but I was going to be limited to the size the Lego imposed, mm precision wasn’t an option. Into this mold was poured terracotta colored plaster. Once dried I had a slab of plaster 128mm wide x 48mm tall x 5mm thick. This was sanded to an even surface as the plaster tends to “creep” up the sides.
Next horizontal lines were carved into the wall with an engineers scribe. That’s just a convenient tool I happen to have but any number of thin pointed objects would do the same job. These are around 4-5 mm apart. I say around because I did them by eye! There are 11 rows of bricks. I’ll let you do the math on that one. Once these were carved vertical lines were carved every other row, creating brick about 7mm wide. Then for the skipped rows the same line was carved between the bricks above. Again, the whole lot was done be eye rather than precision measurements because I wanted the bricks to look different rather than perfectly alike. The aim here is to create a brickwork pattern. Then the gap between the bricks are extended over the edge of the plaster. This creates a complete brick wall bar one flat face (which will become the inside wall)
As a final step the whole wall is textured. To do this I went over each individual brick and took a random shaving off the face. There was one brick that had a particularly troublesome bubble in it, so I carved that out. Then each of the gaps is cleared again with the scribe, and the outer edges of the brick face are slightly rounded to create a worn brick look. The end result looked something like this (I am cheating here in that this is the first cast from the mold).
This seems like a lot of work for one wall, but this will be the master for many walls, and two further masters to come, so it’s worth going that extra mile. Once I was happy with the master I extended the Lego frame out one “pip”. This created a nice even gap around the wall. The master was tacked down on a glass surface, and the mold glued down around it with a silicon sealant. Glass is theoretically easier to clean. In practice, I still haven’t cleaned it property, so it may pay to use a disposable piece of glass rather than something that matters. Make sure any excess sealant is cleaned up from inside the mold as this will become a permanent feature if not fixed now. The whole surface is then leveled. I can’t stress how important this step is. Previous mold making attempts I hadn’t cottoned on to this and it means that the non-horizontal surface results in a lot of sanding on the cast product. Taking the time on this step will save you a lot of time in the future!
I use Pinkysil silicon to make my molds. This is readily available from local craft stores, and reasonably priced. It’s a two part mix, and cures pretty quickly. To figure out how much you need to mix I fill the mold (without the master) with water, then drain that water into a disposable plastic cup. I then weigh it, and halve the amount (because the silicon is a two part mix), and then pour out half from the plastic cup, and mark that point. Then I get a second plastic cup and mark the same level. Remember, if this is more than half filling the plastic cup then you will need something bigger to mix the two parts!
With the Pinkysil mixed & poured into the mold box I finally remembered the camera!
Something you can’t see here is the vibration applied to the mold to remove air bubbles. I don’t make enough of these to justify a vacuum set up, so some vibration of the mold is needed to ensure all air bubbles are removed. My super fancy tool for doing this is a cheap electric toothbrush. I used one of these to make a vibration board similar to this tutorial on Hirst Arts website.
I left this to the next day to cure, and dismantled the Lego to remove the mold.
The master was glued down a little too well, and was destroyed in the process of removing it from the glass. It’s not wasted though as the wrecked pieces will make excellent brick rubble on future projects.
I then set to casting up a new wall from the mold. About 30 minutes later I was able to pop this new wall out of the mold.
Here’s a shot next to a partially assembled Humber IV for Bolt Action. As you can see the wall is pretty much ready for action straight out of the mold!
I have cast up two walls so far and these will be used to make masters for two more wall molds. One with a window and door, and one with two windows. The openings will be left blank allowing for a variety of window fixtures to be added. These too will probably be molds allowing me to make one master, and cast many windows! These will probably need to be made from resin rather than plaster.
While plaster is heavy, it does have the advantage of being easily converted from full wall to ruined wall. Just apply a hammer. I am also hoping that the thin wall section will mean a lighter final product.