Starcrete

The first tiles werent so successful, they turned out to be a little too crumbly to use. They also took a very long time to dry, so I decided to oven-dry them, along with a new mixture.

This was very carefully measured out at 3:1 Perlite / Starlite, I wasnt so careful and left some Starlite in the cup, plus I added the Perlite in half-cups and it wasnt accurate.

This mixture ratio holds together much better, but will take longer to dry.

I pressed some smaller tiles, crushing about twice the volume of the mould into it. This forms a much tougher end product.

I also tried cramming a bit of poly tube full of it and rammed it down pretty good.

This makes a material that is slightly flexible. The mixture is kind-of non Newtonian, it can be bent and stretched a bit but is also slightly springy while wet. It could be trowelled onto a surface with a bit of practice.

After baking the pieces were a bit of a lottery.

Gas Mark 2 for an hour was more than enough to drive the moisture out of the smaller pieces. They cooled in a matter of minutes and were handleable. Interesting...

The moulded pieces remained the same shape and didnt deform at all. The surface turned kind of plasticky and its slightly rubbery inside but breaks open under pressure.

Its more like Flapjack than Cocoa Krispie, smells delicious. Probably isnt... ;-)

The first pieces crumbled when I tired to get them in the oven. Now they are fully dry they are a bit delicate. This ratio of mix could be poured into a cavity and packed but doesnt support  any weight.

However, the test pieces behave as I had hoped.

I hit this bit with a blowtorch for over a minute, and it just looked at me, so far so good.

Next I turned to a fully-dried piece of compressed tile from yesterday that I left on my bench indoors.

This dried out to make a chunk that feels like Papier Mashe.

However it doesnt burn. It doesnt even burn your fingers...

After the first success I tried the cooked moulding, and it doesnt affect it in the slightest.

The Perlite simply adds to the bulk and is completely inert. Being a foam it does not transmit the heat inside the Starcrete at all and improves the handling of the original material as well.

I'm very impressed with the performance. :-D

I managed to get my shit together today enough to make a batch of Starcrete, and now I'm waiting for the test pieces to cure.

Should be tomorrow I'll get some test results then.

I decided to use flour rather than cornstarch; in this application I dont think it'll make a huge difference.

Ingredients

1 Litre PVA

200g Sodium Bicarbonate

1.5 Kilo Plain Flour

1 Litre cold water

10 Litres Perlite

Mix together the Sodium Bicarbonate and a little water to make a paste, then add the glue and mix, then add the water to thin it out. It mixes better this way.

Then add the flour a little at a time until the paste reaches the consistency needed to glue the perlite together. I found I needed the whole bag of flour to make it gloopy enough, you could add more and make it stiffer but I dont think its necessary.

We shall see... ;-)

Take a cup of the stodgy mixture and slowly knead in 2 cups of perlite. This is fun, just like cocoa krispies.

This ratio of mixture makes a nice solid when compressed together.

Here I just grabbed a handful and moulded it into a ball with my fingers. It isnt messy now, the glue absorbs into the perlite and coats it, and it all sticks together really nicely.

I lined a dish with greaseproof paper and piled in some of the mixture.

The first one I just did with my hands, it works quite well but it wasnt very even. But it stays together when wet nicely and made a decent tile.

The next one I pressed down with a bit of wood. This crushes the perlite at the surface a bit and makes it smoother, I'm wondering if a press would work even better to produce even more solid bricks.

Shouldnt be hard to knock something up with some scrap plywood to push tiles out by the dozen.

Here's how tough the stuff is right after mixing. It performed exactly as I hoped it would.

When dry, that would be an artificial rock. :-D

This is using the test ratio of 2:1 Perlite / Starlite.