The Garden Ramblers Blog: Sand-casting Cement Leaves

What is Sand-Casting?

Sand-casting has been around for a very long time, most likely invented before the wheel. The technique is used to make a temporary mold for a wide variety of materials. Today art work and machine parts are made from metal by sand-casting. In the 1970’s, sand-cast candles were a popular craft. Usually wet sand is used to make a form to shape an object. Gardeners today have found this technique useful to make birdbaths and other garden ornaments using Portland cement mixed with other aggregates. Sand-cast leaves are popular today as a way to make one of a kind birdbaths and garden ornaments.

Let’s face it, if you pour concrete on a leaf, it will be flat as a pancake. This is great if you want the fossil look or a stepping stone, but sand can be used to shape and support the leaf. You can make the leaf look natural or shape it in to a birdbath or part of a fountain.

There are many types of sand and it will depend on what’s available as to what you can use. I like to use fine sand such as sand blasting sand to mix with the cement. This sand costs a little more but the fine texture picks up the veins of the leaves very well. I use a coarser textured sand to form the mold. This could be play sand, construction sand or good beach sand. Any sand that holds a shape when damp will work. Play sand will work for both applications. The molding sand can be used over and over. For this reason, I like to cover the sand mold with light weight plastic to keep the concrete out. Some people do not do this and little globs of concrete will contaminate your molding sand and must be sifted out.

collard leaf

If you are going to reuse the leaf, then cover it with light weight plastic too. Cabbage and collard leaves can be used several times.

This is not rocket science, there are many different mixes for sandcasting leaves. But first let’s go over a few terms.

Cement or Portland cement is the basic ingredient of concrete, mortar, stucco, and grout developed from hydraulic lime. Cement only hardens by reacting with water. It comes in grey and white.

Aggregate is anything added to cement, usually rock and sand. Cement plus aggregate equals concrete. Other aggregates could be broken glass, marbles, vermiculite, perlite, PermaTill, sea shells and peat moss.

Curing is the process which concrete or cement hardens. Water must be present for the reaction to occur and usually takes a minimum of 14 days. Keep your concrete piece wrapped in plastic and moist in a cool spot to harden.

Additives or fortifiers can be added to make the piece less likely to break. It is usually made from acrylic or polymers.

Cement dyes can also be added and looks better when using white cement. I like the dry dye but the liquid dye is ok to use. I usually add the dye to the water.

Formulas, I like to use 1 part Portland to 1 or 2 parts sandblasting sand with some acrylic fortifier added about 1/8 part or less.

I also have used thin-set mortar mix. It has the fortifier and sand in it but more sand can be added. Thin set also comes in white and colors. Thin-set also comes in smaller bags.

Add enough water to get a paste as thick as peanut butter. After mixing, slam your bucket on the ground a few times (5-6) to get out air bubbles in the cement. Tiny air bubbles forming near the surface of the leaf can ruin a project. Let the mix sit for 5-10 minutes before applying to your leaf.

Safety. Cement is caustic and will irritate you skin, eyes and lungs, use a dust mask, safety googles and rubber gloves when mixing and forming.

Leaf Selection. I like to sand cast in late summer when leaves are big and sturdy. You can sand cast in the winter with cabbage, kale, collards and house plants. Look at the back of your leaves for prominent veins. Banana and English ivy leaves are too smooth. Also leaves should have a smooth outline. Red oak, Sweet gum and endive –not so good- the points will break. Some good leaves to try – hosta, begonia, rice paper plant, piper plant, catalpa, lotus, elephant ear, dogwood and water lily. Any heart-shaped or round leaf will work very well.

Arlene with a cement rice paper plant leaf

Appling the cement to the leaf. I like to make a mud-ball with enough cement to cover the leaf. Set the mud-ball in the center of the leaf and press gently to the edge of the leaf. The center should be thick, 1 to ½ inch and the edges thinner. Be careful not to go over the edge of the leaf. If the cement mix is too wet, it will slump over the edges. If this happens, let it set a little longer and try again. Use an old paint brush to smooth the cement and sign your work.

Finishing Let your project set up for 4-5 hours or overnight. Carefully lift off the sand using both hands. Your leaf will be very fragile for a few days until it cures completely. You will be tempted to pull off the leaf but please wait. Check the edges for over runs and rough edges. Now is the time to file off imperfections. There are special files for concrete or just use an old wood file. I like to use a Dremel with a tile cutting bit to smooth the edges.

Peel and Reveal. When you are satisfied with the leaf edges gently pull off the leaf. Don’t worry if some veins get stuck they will rot away soon. Gently rinse with water and wrap in plastic and let it cure a few days.

Sherri with an elephant ear ready to peel

Painting Outdoor acrylic craft paints or house paint will work great for your leaf. Use a dry brush to clean your cement leaf first. Brush the surface with a damp brush before applying paint. Solid colors are boring so add many shades of the same color. To make the leaf veins pop let the base color dry and brush on a darker color and quickly wipe off with an old damp tee shirt.

Add Ons Before the cement dries, a stiff wire can be added to the back to hang your leaf. Attached with a small lump of cement. If you want to place your leaf on a ½ rebar post add a ½ copper coupling. Make a golf ball size ball of cement and place in the center of the leaf. Push in the brass coupling about half way.