I'm thinking about casting my own window sills and thought I'd check if anyone has some tips about it. If it matters, I can mention that the outer walls are made of lightweight concrete.
Some considerations:
- Should they be cast in place or cast in a separate mold and then mounted?
- Can they look nice - assuming you think concrete looks nice? Should you sand them after casting to get rounded edges perhaps?
- Is it practical - what happens if you spill plant water on them?
- Do they need to be treated in some way - "impregnate" or "oil" them perhaps?
What do you think? A crazy idea or a cheap and good way to make window sills?
Some considerations:
- Should they be cast in place or cast in a separate mold and then mounted?
- Can they look nice - assuming you think concrete looks nice? Should you sand them after casting to get rounded edges perhaps?
- Is it practical - what happens if you spill plant water on them?
- Do they need to be treated in some way - "impregnate" or "oil" them perhaps?
What do you think? A crazy idea or a cheap and good way to make window sills?
Hello. I would have cast them, i.e., nailed together a form next to it.. To get nice edges, you can use different moldings, a tip is a minimal triangular list that is attached to the edge where the finished top will be. When you remove the form, you have a neat little beveled edge, which is also strong, i.e., withstands most bumps and pushes. Oiling them afterward is probably a good idea, I haven't done it myself, but I know it's popular among those who cast their own countertops.
Regarding sanding, you can smooth the top with a steel trowel, but you'll probably need to sand the edges a bit...
Regarding sanding, you can smooth the top with a steel trowel, but you'll probably need to sand the edges a bit...
yes Kalleman, but it is generally more difficult to build molds in steel/sheet metal... Plastic that is placed in a mold usually crumples no matter what you do... and who has access to real plastic molds?
becomes visible in the concrete
Do you think it is necessary to vibrate the concrete properly for it to turn out well, or is it enough to tap a bit on the form?
If one is going to trowel, how is it done? Renting a "helicopter" for a small windowsill feels a bit wrong, doesn't it? Maybe there's some kind of grinding disc that can be attached to a regular drill or something similar?
Does anyone know where to get pigments if you want to color the concrete dark gray or maybe black?
If one is going to trowel, how is it done? Renting a "helicopter" for a small windowsill feels a bit wrong, doesn't it? Maybe there's some kind of grinding disc that can be attached to a regular drill or something similar?
Does anyone know where to get pigments if you want to color the concrete dark gray or maybe black?
I built a simple mold with brass sheet that I found at Clas Ohlson. Steel sheet would have been cheaper, of course, but the pieces I found there didn't have the right dimensions + I didn't need much. The result exceeded expectations with an almost silky smooth finish on the concrete. I didn’t have a vibrator, so I gently tapped the mold for a few minutes after pouring. Steel sheet can be quite easily bent and placed in a mold.Milkshaken said:
Other materials you can use include old window glass, plexiglass, building plastic as mentioned, regular form plywood also gives good results. I also saw the result of a classmate’s casting who tried casting against aluminum foil which is not recommended. The foil was completely gone after about a day in the mold with discoloration and strange surface texture on the concrete as a result. Aluminum cannot withstand the high alkalinity in the concrete. Even my brass was heavily oxidized after a day.
Why not cast against something like plywood or veneer and get an exciting wood-grained surface?
Sift out the coarse material in fine concrete and get a "perfect" even gray surface without irregularities.
Coloring concrete requires LARGE amounts of pigment and often still doesn't turn out as you expected. Especially if you're aiming for black concrete. The result is highly dependent on the color of the cement and the aggregate. It's best to start with white cement and aggregate close to the color you want. Completely black is probably impossible without ruining the concrete's strength. Otherwise, you can buy pigment in regular paint or art stores. Artist pigments are of much higher quality and class but more expensive.
"Äntligen hemma" made a concrete countertop, and sanded it with water sandpaper, then sprinkled "fine cement" (poured cement into a sieve to remove any "lumps") for the final finish.
It turned out very nice if you like this.
Might be worth a try.
Good luck!
It turned out very nice if you like this.
Might be worth a try.
Good luck!
I would not have been satisfied with just knocking, I would have reinforced with rebar. And then I would have induced vibrations with some machine..... Air is a plague, you have to get rid of it completely for full strength to be achieved. Remember that a windowsill should not be more than about 15-20 mm thick...
Reinforcement, of course, and then not using regular fine concrete, which is quite viscous, but rather a free-flowing product that doesn't need "vibrating", to guard against air pores.
At ÅF for the big ones... check out Rep 920 or EXM 702, both from maxit. Don't forget to read the product sheets so there won't be any mistakes in the end 