I've spent a number of days pondering and researching the best way to construct the "bath" part of my bird bath. The column was a no-brainer, since I've got the two planters. But there are a number of options for constructing the top.
The simplest is to get a terra cotta saucer--the type you put under a potted plant--seal and mosaic it. Heck, you don't even have to mosaic it. You can plop it on the top of the base and be done. That is intriguing, but not exactly the style I want.
I wanted to construct something out of concrete instead, and even with that decision made, there are choices.
The two most common methods of constructing a bird bath from concrete is to either use a mold, or sand cast the top. I've searched the internet for bird bath molds and really wasn't crazy about the style of them. They can also be very pricey, even though you can make dozens of bird baths out of them. I tossed that idea pretty quickly. As for sand casting...that has never been a method of concrete construction that intrigues me. It seems the sand would be a big mess--you've got to get it good and wet, yet more work than I need. You construct it upside down, so you never really know what's going on underneath until it's too late. And for this method, I'd need to get my hands on flexible fiberglass mesh as my reinforcement. I wasn't able to find any fiberglass mesh in a roll that costs under $60. I also saw some articles that state some types of fiberglass mesh break down against the acidity of concrete. Too big a hassle.
That left me with two other options: Making an armature, or making my own mold.
These were the options I pondered for a while. My first choice had been to make my own armature. My only problem with that is I want perfection in the shape. I'd like to have a clean edge that I could tile. And getting hardware cloth or diamond lath to sit perfectly flat is a challenge, especially given the size I'm trying to deal with. I could do it for sure, but I couldn't get over the idea that there had to be an easier way.
Then I found it: On a website called Nothingbuthardware.com.
Fill the 20" round with about 1/2" (or less) of concrete, adding a disc of hardware cloth for my reinforcement. Place the 16" saucer in the center, weighted down with a brick or sand or rocks or something. Fill the space around the outside of the 16" saucer with another 1/2" of concrete to form a "bowl".
In theory, this should give me a 20" top with a flat 4" rim around it. That 4" edge will be the outside (blue and white) pattern below. In the middle of that will be a 16" bowl 1/2" deep to make the inner circle.
It seems really easy. I don't know if it will be. The saucers were cheap. They cost less than the shipping. I'm also gambling that they are as perfectly smooth as they're shown in the picture. AND I can reuse them as stepping stone molds or more bird bath tops if the need be. Like Alton Brown says on Good Eats: Multi-taskers are good. Pouring the concrete in a mold should give me that perfect edge I'm looking for that would be difficult with armature or sand casting.
So, that's my plan. I am now in wait mode as I wait for the tiles and forms to come in the mail. In the meantime, I'm making butterflies on rebar posts. Maybe I'll post some pictures of those this weekend!