Try sand and Portland Cement - I am not sure what you mean when you say cement mix. Portland come in a 90lb bag and has no gravel. I use 1 part portland to 3 parts sand. The rain probably helped -
When this mix cures - it should be damp ( keep covered with plastic for several days). If you allow it to dry too soon ( uncovered) , it might crack as you described. If they are broken - completely in half - try liquid nails for concrete. If it is just a crack - portland with a little water in a paste may fix.

As Mike said, you need to be specific in what ingredients you used. I'm assuming on the sand that it was the Quikrete brand bag of sand but haven't a clue what "cement mix" is. Or are you using Quikrete sand/topping mix? See, it can be confusing.
Other causes for the leaf cracking can be that the cement mix was too thin, you didn't give enough support to the leaf when turning, didn't cure long enough before turning, didn't mix your ingredients correctly, too much water. Rhubarb leaves have those nice big veins and if the cement mix isn't thick enough or reinforced it can crack along the veins. Billie

I think I found out what the problem was. billie ann, yes, it was the quikrete sand/topping mix. It worked great for the calla lily leaf. When I mixed for the rhubarb leaves the mix in the bag was beginning to get hard. I chipped it out and crumbled it with my hands before mixing with water. My husband said that when the mix begins to get hard in the bag it's no longer any good to use. I did put on a thick layer and I sure the mix wasn't too thin. I'm going to get a new bag of mix. By the way, one member on GJ has used mortar mix. Have any of you tried that?

Here's my calla lily leaf.

{{gwi:72031}}

If it cracked down the middle vein you could still use it in your garden. Just put the cracked edge in the soil long ways. It will look like half the leaf is buried, no wasted project.
Paws

Holy mackerel, is that the original Paws? Billie

Beautiful leaf!

Sorry, got sidetracked by see "Paws".
Great leaf casting!
Your husband is correct about the cement mix hardening in the bag. Humidity in the Summer or storing bags directly on a cement floor can introduce moisture into the bag.

yes billie it is me....been in hiding...remember there are no flops, use the old nogin and you can come up with some interesting things.
paws

Hi all!
I'm Monika feom Italy. I would like to learn to make some birdbath with big leaves. Can you tell me what book/DVD should I buy to learn this technique?
Thanks for any help!
Moni

Try this link Monika.
http://www.carolinahosta.org/newsletters/LeafCasting.pdf
Paws

Laura,

Your leaf is stunning! What did you use to paint it? I love that look...so soft and perfect!

becky

Becky, I used Patio Paint thinned a little with water. Painted it green, then dabbed it little with amber/yellow.
Paws, I used the cement/sand topping mix for 5 leaves. All of them broke except the one in the photo. I'm sure the first 2 broke because the cement had began to get hard in the sack and I used it anyway. I don't know why the last 2 broke unless I didn't let them set long enough. They were Ok until I picked them up and set them on the garage floor. A couple hours later my husband told me one had broken in two at the center vein and the other broke into several pieces.

Can anyone tell me if I made a leaf birdbath out of concrete, but did not make it thick enough, (due to an appointment I had to get too) Is their anyway I can make it thicker now, or can I make it thicker with a hypertufa mixture on top of a reinforcement wire..???