I am making a cat bed using macrame cord with Elmer’s Glue-All mixed with water, and a giant beach ball as a model. I want it super stiff so it keeps its shape. What can I use?
I should mention I’m not doing a typical criss-cross pattern; I’m wrapping it from the top to half way in the round. It’s a huge beach ball, 32 inches. I just want to make sure when I deflate the ball the cord stays in place. It doesn’t matter if it looks like macrame cord.
You haven't had a chance to answer the questions yet, but I'll just toss in some ideas (the reasons for some of the questions will become obvious).
Use multiple layers. Wind the first layer and let it dry enough to be stable but not bone dry, then put another layer on top (you can wind into the valleys between the cord rings in the first layer). This will still look like macrame cord but will be more than twice as stiff because the thickness contributes additional stiffness.
Get a large plastic serving bowl and use it as an insert/liner to keep the shape (it doesn't need to be the full height or the exact same curvature or diameter). It doesn't need to be super-rigid; something in the "disposable" category will help keep the shape. If it doesn't want to stay in position, use a few dabs of hot-melt glue to keep it from moving around.
Coat one or both sides with clear epoxy resin. After the Elmer's is completely bone dry, brush on a thick coat. After it cures, if it still isn't stiff enough, add another coat. The coat doesn't need to be super-thick to add a lot of stiffening. Downside: this option will make the cord look like it's coated in plastic. Upside: it will be very easy to clean.
If it's acceptable for either the inside or outside to not look like macrame cord, cover the surface with a few layers of paper mache or a layer of paper mache clay.
Superglue (cyanoacrylate adhesive, the thin stuff). Do this outside because it will release a lot of bad fumes. Cotton is one of the materials superglue reacts with to rapidly cure. If you saturate the cord with superglue, a lot of it will soak in, then rapidly harden, turning the cord into hard, stiff plastic. It will take a lot of superglue for something this size (just guessing on the order of maybe a pint bottle or more, so it will be an expense; calculate the volume of cord in the bed and you'll need close to that much superglue).
Wrap the beach ball with a sheet of polyethylene as a release agent (e.g., polyethylene sheeting or sheets cut from plastic grocery store bags). When you wind the cord, don't pre-saturate it in Elmers. Just use a method that keeps the windings in place (e.g., periodic spot of hot melt glue). Once the winding is complete, saturate the cord with superglue (I won't cover all the reasonable precautions here). It will turn into a hard, stiff plastic bowl that looks like macrame cord.
You could do a quick experiment with a short length of cord to see if you could substantially reduce the amount of superglue needed but still add significant stiffness (I've never tried it the following way): Make the bed with the Elmer's as planned (wrap the beach ball first with polyethylene). Once the Elmer's is completely dry, the cord may still be porous enough to absorb some superglue and harden.
I believe epoxy and superglue are pet safe after they're cured. But cat smelling ability is better than people's. If you use either, give it several days after you can no longer smell any chemicals before gifting it to the cat.
If you use baking soda with the super glue it will set rock hard. Sprinkle baking soda first, then saturate it with super glue. Do that in layers until you get the hardness you are looking for. Try it on something else first because you will be surprised at how the 2 react together and become like concrete.
