Acrylic Brick Molds
I found these 2 pieces of 3/16" thick acrylic at work in the trash.
They have a slippery feeling plastic coating . I'm going to try and make a brick mold to see if aircrete sticks to the plastic or not. I will try and design it so it can be opened up and closed in case it fails !
I'm trying to figure out the best way to put it together that will be easy to take apart and be reusable.
It measures 14" long by 12" high and 8" thick. If I were building a dome I'd want no less than 8" thick bricks so I went with that.
Does anyone know if silicone glue is sticky to aircrete? What about spraying the mold with WD-40?
I decided to attach the corners on one side with pop rivets, and use self tapping screws on the break apart side of the corners.
They easily come out with a cordless drill.
I'm going to use a piece of scrap aluminum plate for the bottom, and use the same self drilling screws to easily remove the bottom.
This will test how well or not aluminum separates from the set-up aircrete block.
I pre-drilled the holes through the plastic to prevent cracks.
@upwinger The plastic forms could work. If it's slippery, you would not need any hinges. You would just slide it out. No problem. Let me know how it goes.
@KnowItAllTeen Thats what Im hoping for, but not sure . we'll see soon.
Im going to go tomorrow and try to find some portland cement, sticky stucco ( or scratch coat) mix
and clothe. And Cat food
The aircrete stuck to the plastic and leaked out at the bottom.
I will try again after removing the plastic film from the acrylic, and try running a bead of silicone glue
at the bottom of the mold.
The brick wont slide out, so the mold needs to be rebuildable. The mold broke apart no problem, but the aircrete that stuck to the mold
caused the brick to break apart at the bottom.
Hope the next attempt goes better... I just have to wait for the rain to stop for a few days.
@upwinger What if you were to line the mold with a thin slippery plastic liner? In theory it would prevent leakage and release from the mold. Then you could peel the liner off of the aircrete.
@Zander I was thinking " what if I sprayed the inside with Pam cooking spray"
@upwinger Oil it up just like a brownie pan!
I am going to try this weekend again after adding an acrylic bottom piece and plastic wrapped the inside of the mold
for "Take 2" !!
I had only one small blow out leak at one corner...
Next block I will assemble the mold with a bead of silicone under the plastic wrap so the sides will squeeze a seal when I screw it down.
The plastic wrap works great for the block release, except it's hard preventing the wrinkles. I haven't tried removing the block from the mold yet, but I used the plastic wrap on one of the mushrooms and it slid right out of the bowl.
I'm planning on using these test blocks to make some miniature Rapa Nui' Moari heads:
The block weighs in at exactly 20 lbs on my bathroom scale:
Does that sound about right for aircrete density?
Brick #3 has the best density so far. I don't have a hardness tester but I can't push my thumb into the brick at all and feels to be a nice dense hardness.
For my next test brick experiment, I'm going to see if I can "pre-skin" the front and back surfaces of the brick with weed clothe, to see if the aircrete will bond to the skin while curing in the plastic wrapped acrylic mold. If this works, it would be possible to make a pre-made dome and just mortar the blocks together like an igloo. I'm thinking if there is a "flap" of overlapping clothe on each block, it would help hold the bricks together when you glue them together.
BTW, The rubber weather stripping tape sealed the bottom of the mold perfectly and there was no blow out leakage on this pour.
My aircrete planterbox is slowly coming along.
The dots on top are the rain drops that started just as I finished. I covered it with plastic as quickly as i could!
The "cracks" on the sides are actually wrinkles from the plastic wrap lining the mold.
I think I will try to leave one surface unwrapped on the next pour, and just spray vegetable oil on it to test.
@upwinger Excellent work! Imagine the polyester sheeting around the brick before it's even apart of the dome. It might be a better option for maintaining the structural integrity of the brick. It might take more time however. Guess, I'd have to test that when I have the chance.
I've just completed the proof of concept experiment for preskinning an acrylic form...
It feels alot like drywall. I can pull the skin off if I try, but it feels pretty glued on after 4 days of curing in the mold. I just removed the block today and it released super easily. I sprayed the insides with cooking oil spray and that made using plastic wrap unnecessary.
I think plastic wrap still helps to prevent blow out leakages at the bottom, along with rubber foam weather stripping tape.