Concrete Leaf Casting : First Attempt

Somewhere in the last couple of years, I encountered a post about concrete leaf casting, and haven't been able to shake the idea out of my head since then.  I was quite interested to try it last summer, and read several posts about how it's done, and the ingredients used.  I also am fortunate enough to have a Gunnera plant in my garden, which seems to be getting bigger leaves every year, and which would make an awesome concrete leaf, such as this amazing creation by Little and Lewis on Bainbridge Island, WA:

Even if mine were half as awesome, that would still be very amazing.  So with this dream simmering in my head for a couple years, and the recent realization that Fall is around the corner, and that the cooler temperatures would be suitable for such a project, I decided to finally take the plunge, and try it out.

I don't know how to post yet, since I won't really know for a couple of days whether it worked or not.  It felt like a disaster almost every step along the way, but I am still hopeful that it worked out, and will be as amazing as I have dreamed.  So I will post what I did and learned so far, and then once I know, I will post the results, and perhaps this post will be a useful lesson in either what to do or what not to do.

Challenge : Find the materials.  Most "recipes" for concrete leaf castings were something like : 1 part Portland cement, 3 parts sand, and some part water and/or bonding/fortifying agent.  But as I suspected, the brands and products mentioned were not available locally, so I did some investigating on the Home Depot web site, and went to the store with various product descriptions in my hand, hoping to finalize the decision. I came away with two bags I couldn't lift : 88 lb of Portland cement, and 80 lb of jointing sand.  I had investigated various mixes, but all included some gravel in the mix.  I wanted mine to be a fine mixture, so I chose to mix it myself, and also chose the finer jointing sand rather than construction sand.

The Home Depot store didn't carry the acrylic based bonding agent which I was seeking, but I persisted, and phoned the number on the web site, and asked them to track down the product, which was a Stone Mason "Acryli Bond" liquid.  Sure enough, we found a store not too far away which carried it, and I was able to pick up a 4 L (1 gallon) bottle.

Challenge : Dust masks.  They were advised for the mixing of the Portland cement, which is a fine powder.  Good thing I bought a 3-pack, so my son & daughter had fun trying them out.  Since I couldn't wear mine.  I felt like I was being suffocated, it was too hot, and my glasses steamed up when I breathed.  So after trying a few times to use my mask, I gave up on it, and just held my breath when scooping the cement, and tried to mix carefully.  I pre-wet all the sand, so at least it was not dusty at all.

Here's my daughter on the porch of our shed, where I was setting up the Gunnera leaf on plastic, and mixing up my sand and cement in the wheelbarrow.  The wheelbarrow was a good idea.  I wouldn't have managed with the deeper bucket I had originally planned.  And it washed up really well afterward.

Mistake : While the porch was a great idea since it is covered to provide protection from sun or rain, and the leaf could be left there (since I can access through the one door) for a number of days, it was not at a good height for my back.  Very quickly I found that my back was very sore bending over to work on it.  The wheelbarrow too was too low, but I managed okay by kneeling beside it.  The other problem was that it was hard to reach the back part of the leaf.  Access from all sides would have been much better, such as on a sturdy old table.

Challenge : The concept was to mound of the sand to support the upside-down leaf, so when it was done, it would be a naturally cupped shape.  But the Gunnera leaf I chose was quite cupped, and the amount of sand I would have required would have been more than half of my 80 lb bag!

My solution was to use instead some pots (they were nearby) to support the leaf, and use some sand sparingly in between.  There were a few places the support was a bit light, but since the Gunnera was a very stiff and strong leaf, I'm hoping it was adequate.  We'll find out when we flip it over, and find out if I had ripped or distorted the leaf too badly.

Mistake / challenge : Choose a small leaf to start.  I didn't.  I didn't feel that I had time for that.  And I suspected that if I tried a smaller leaf, I would find so many challenges that even if it turned out okay, I may not be "up" to the big project, knowing what I was truly walking into.  Perhaps that's true.  But it would have been comforting to know what I was doing, rather than feeling on the edge of disaster through the whole process.

I had read to apply a wetter layer first, and work it into the small wrinkles and crevices in the leaf, before applying the thicker concrete.  This seemed to be a very good idea.  Especially since the sharp slope of the leaf (a flatter one would have been better!) made the concrete slide quickly off.  So being able to work a thinner layer in would prevent some of the air bubbles I'm sure I would have had otherwise.

Challenge : Reinforcement.  This photo doesn't show it well (click for a larger view, perhaps it will show better), but I used 4 pieces of 1" chicken wire to reinforce the leaf, once a thin layer of concrete was applied.  The challenge was that it was difficult to bend it into a shape that matched the deep ridges and valleys of the leaf.  If I didn't make it snug enough, I couldn't cover it in concrete, which would result in chicken wire showing at the back.  If I pressed it in too far, the sharp edges broke through the leaf, possibly resulting in wires sticking out the front of the leaf.  So I struggled for a long time with this step, with my husband trying to help with cutting and bending also (I had called for his help when I started the concrete and realized I forgot the roll of chicken wire in the garage).

Then I spread the concrete over top, using a small metal coffee can to scoop it from the wheelbarrow.

Challenge : Unhelpful help.  If you have any "helpers" nearby, best to communicate with them about what you are doing, and how they can help.  Sadly, when I didn't notice, my husband added more water to the wheelbarrow to "help" me.  But I wasn't using water at that point, I was using the Acryli Bond liquid.  And mixing the sand and cement first then adding liquid, was a better order (so the cement wouldn't clump up right away).  I should have just scooped as much water back out as possible, but I decided to try to add more cement and sand to it, to get the consistency right.  I ended up finishing up my whole bag of sand, adding more cement, and finally got it to a workable, although still too runny, state.  Then I added some more Acryli Bond also, to make sure it would be strong enough to hold the fine edges.

Here is the finished product, about 2 1/2 hours after I started out.  I finally managed to cover the chicken wire, and get a reasonable layer of concrete all around the leaf.  It kept running down into the valleys, and I needed to work it back up onto the ridges.  I think the finished thickness was somewhere between 1/2" to 1" thick, but since I used up the 80 lb bag of sand (other than the part I had laid underneath), and maybe 30 lb of cement, then I guess the whole thing will be over 100 lb to lift!!  Wow, I guess I thought about that, but the reality had not sunk in...  I will need help to lift & flip it over!

I understand the concrete cures better when kept moist, so I flipped up and laid plastic on it.  Today I visited it.  I have no idea how to tell if it's finished setting, so I may give it a couple of days.  I sprayed it with water, and left it sleeping inside its plastic blankets.

Who knows what monster - or artistic wonder - lies sleeping there?  I will know in a couple of days, when it is flipped over, and the leaf peeled off.

[Aug 31 : See result, which was not as I hoped].