Looks like I overshot my mark on picture size. I reduced to 20% of the original, guess that wasn't enough.

I don't know the answer to your specific question, but I do have information I got from a home improvement show. An old Italian guy was doing cement work. He said the biggest mistake is too much water in the mix. Too much water makes concrete weak. He grabbed a handful of his mix and squeezed it. He said it should be wet enough to hold together if you clump it, but almost dry looking, like sand, not soupy.

I tried to mix it like he did when I used Quickcrete to patch mortar all over my house. It held up very well last winter despite terrible below zero weather. Now I had heard our city inspector tell a guy not to use Quickcrete to patch because it would fall apart in the spring after the freeze and thaw. But my patching held up beautifully.

I don't remember getting bubbles, but I used regular Quickcrete.

ps - your leaves are beautiful with or without bubbles

Gardengal, There are many reasons for "bugholes" in your leaves. It can be too much water in your mix, air trapped between the leaf and the mix(yep, even if you work it there's air), working the mix to much either in initial mixing or working it on the leaf. Even the pros get bugholes, they just repair them or not.
I use a mortar mix of portland cement, sand and water for leaf castings. I use some type of reinforcement for pointy leaves. I'm curious why you're making two layers on your leaf castings.

Flowerkitty, Just so you know "QUIKRETE" is the manufacturer and makes lots of different products. What "regular" QUIKRETE product are you using?
By the way Gardengal, great castings! Billie

Here is a link that might be useful: Quikrete

Billie ann, I used two layers because the "resurfacer" had only water added and I was concerned that it was not strong enough. I think you are right about using too much water. Thanks for the feedback. I'm looking forward to painting my leaves.

Your edges are wonderful! Wouldn't it be great to get perfect edges AND no holes on a leaf!
Laura

Laura, after a 2 day curing period, I pulled the plant leaf off and supported the concrete leaf on the sand bed and used a steel file to clean up the edges. I used drywall mesh tape to reinforce the edges (plus a few strips crosswise and lengthwise). Some pieces were sticking out and I used my DH's stone power grinding bit to clean that off. (can't think of the name of that tool).

Without the little imperfections they wouldn't look real. Also some like this lantana leaf, have something in the leaf when released into the cement retard the curing. You can make it look distressed or bug eaten. Holes in leaves used in a fountain give more movement to the water. You can use peat moss in a recipe to add more holes. Billie

Here is a link that might be useful: {{gwi:2565}}

I have no idea. But those are great. I may try it next year.

The fortifier may be causing too much air to be entrained in the mix causing the bug holes.

The mix of portland cement (BRAND doesn't matter, it's all portland cement), sand and water is all you need to get good castings. Good idea using the mesh at the thinner ends. Mixing up the mix too much will cause air to be trapped. When mixing concrete think of it like a cake mix...the more you whip it up, the air-ier it gets and rises (causes bug holes). Concrete too wet will be brittle, too thick will cause holes. A good mix is mud-patty or pancake consistency. Slather it on and don't pat it too much.

My DH has been in the decorative statuary business for many years, and there is a BIG difference between decorative STATUARY and pouring foundations or other flat work.

Gardengal,
I find a mix of 1 part cement and 3 parts sand works well. I have also used the Type S mortar by sakrete, which is similar to some high strength mortar mixes , and can also be thinned to make a re-surfacer.
The leaves you pictured are different varieties. The one with the surface poking may be inherent in that particular type leaf as well. I would be curious if you have tried that particular type leaf again with different results.
I have made lots of leaves and there are some that pok due to fuzziness or I think the sugar content of the leaf.
Very nice leaves!!
Dena

I have tried about 8 or 10 leaf castings with vinal patch and only 2 have turned out. I think I also may be adding too much water. The two that did hold up are beautiful!!
I am going to try today with a little less water and leave them sit for a little longer before removing the leaf to see if that helps. I want to get this perfected before the big leaves come out in my area!!

Those are the BEST leaves I have ever seen! Good Job!!!

It's the sugar content in the leaves that cause the little pock marks. If you apply your concrete mix directly to some leaves, there is an actual chemical reaction between the leaf and the concrete mix. If you find a variety of leaf that you like the shape of but know that it will leave a rough surface, use a dry cleaner bag over your leaf and apply the concrete to that. The dry cleaner bag is thin enough that you will still get the leaf's detail but a much smoother surface. Plus, you have the added advantage of possibly being able to use the same leaf for casting more than once.

Early in this forum, there was a story of how contractors used to put the small pea gravel on top of the poured concrete for texture and effect and to get more of the pea gravel to show, they would pour coca-cola on the top because the sugar in the soft drink would eat away enough concrete to expose more of the pea gravel.

Your leaves are great! I use leftover pieces of concrete to file my edges smooth but using the metal file makes a much neater edge.

c