Concrete casting question

[Mark]

Can anyone tell me how this concrete post cap was created?

Thanks

-Mark

[Mike]

Could have been factory cast.

[Bob Morrison]

Probably cast upside down in a metal form. Looks like a cement rich mix with pea gravel and possibly a medium or high range water reducer to reduce shrinkage and cracking.

[ke4fxc_at_knology_dot_net]

mark, look into the way they make concrete counter tops some use formers with all the detail in place like split pvc tubing and plugs through the concrete to make mounting holes for fixtures to the concrete. The molds can be a negative like the way the caps were problem made.the form should be very slick like melemain (sp). use wire mesh and or rebar like in any concrete work for strength. this is a touch on how the system can work. There are books and info on the web and your local big box home inprovment stores. hope this helps with an ideas.

Charles The LURKER :)

[RicodJour]

I could tell you how to make that as a concrete cap, but I'm not sure that it is concrete. There appear to be seams in odd locations for a concrete (seamless) pour. Are you sure it's not a built-up limestone cap?

R

[Mark]

I am not familiar with the concept of a "built-up limestone cap." So no, I am not sure.

[dpb]

...

I certainly agree w/ Bob M that it surely looks cast and not poured in place.

But, I couldn't even decide for certain it's really concrete although I finally decided maybe it was from the last picture in which I decided the markings in the side _might_ be some small air pockets or gravel. Some of the pictures looked like it was actually a granite or similar stone (I don't think limestone, too much "figure"), and there was the one with what appeared to be either a form mark or perhaps a seam??? So much variability in lighting and contrast from one to the other left me wondering just what I really was seeing and not at all sure about the actual material. But, I'm virtually positive with the others it wasn't poured in place but something either cast or cut.

[Mark]

Yes, they are small air pockets.

I'm quite certain this is concrete. The brown color is uniform, and there are casting/form marks. I agree that it is most likely cast concrete.

[Italian Mason]

Most definatly concrete. the smoothness is achieved by a combination of vibrating the form and the actual form itself. This can eaisly be reproduced using trim moulding (for the edges)and dimentional boards

2x4's or whatever thickness is necessary > Can anyone tell me how this concrete post cap was created?

[M&S]

I agree, definitely cast, no trowel touched that piece especially on the edge profiles. We have cast cap stones similar to this on a few occasions. Our technique is much like you have posted. Formwork, caulk, paint/sand/paint/sand etc. We use an SDS hammer and an old chisel with the end cut off and a crutch tip over the end to vibrate. We set the form on thin piece of foam rubber, hold the hammer against the form and hammer a bit. If I were going to make several making a master out of hydrocal or some other very fine plaster and then a latex mold from that master would be my choice.

Mark