Having created several sculpted concrete features with a welded rebar or wooden armature, I thought I would try a very basic method using found cardboard and masking tape.
Step 1: Visit an Appliance or Furniture Store for Cardboard
I found several 2-ply boxes that they were more than happy to donate. This double walled shipping box was a bit tough to cut, but with a sharp blade every 10 cuts or so, it was quite manageable. Very rigid when assembled.
Step 2: Layout Drawing
Having a nice sunny day I spread the box on the lawn and broke the dog sculpture down into 3 major components: body, snout and legs. Ears and hind legs were quick attachments. I added flanges to the basic shape to create the depth of the units.
Step 3: Tape Up Torso
Once the torso with flanges is taped up, flip over to trace out the remaining side. Tape to existing unit. Torso complete.
Step 4: Legs and Snout
I laid the torso in profile on the flat sheet of cardboard and drew out the legs and snout. Adding flanges, I repeated the process from the torso and created two legs and a snout. Using lots of masking tape, I attached to the units to the body.
Step 5: Coming Together
This shows the patterns cut from the cardboard and the dog armature starting to take shape.
Step 6: Fully Taped
The armature is ready for fiberglass taping and is getting checked out by the Canine Inspector. At this point, I have used one free cardboard box and half a roll of 2" masking tape.
Step 7: Fiberglass Mesh
While I have done a bit of sculpted concrete, I have always used expanded metal lath on a steel armature. I wanted the cardboard to have a bit of "tooth" so I covered the unit in self adhering drywall fiberglass tape left over from a renovation project.
Step 8: Scratch Coat
I used basic mortar mix from Home Depot. $6 for a 50lb bag. I half filled a 5 gallon bucket with the dry mortar mix and slowly added water. Before mixing with a drill and paddle mixer (you can use a wheelbarrow or even you hands) I threw in a handful of fiberglass , available from any concrete or masonry supplier. About $10 a bag. I used 20% of the bag for this project, so very economical. The fiberglass mixes with the mortar creating a very strong coating.
Step 9: Apply Concrete to the Armature
Wearing protective gloves, I applied the mortar mix by hand. I try not to add too much water and work with a mix consistency of thick molasses. The mix would dry too fast under the sun so I moved the sculpture under some shade to extend the working time of the mix. At this point, I didn't bother to smooth down the concrete but left all ridges and rough spots to ensure the top coat sticks.
Step 10: Apply in Stages With Deep Undercuts or Angles
The concrete was having a tough time sticking to the bottom of the snout and torso so I gave up and waited until the next day. I flipped the dog over and continued to apply the scratch coat. I let it dry in this position under a tarp.
Step 11: Moving Day.
After the sculpture was totally covered with the fiberglass reinforced scratch coat, I sprayed it down to keep it damp and covered it with a tarp for a day. The next day I placed it on our garden cart and moved it to where it would live in our yard. I wanted it in place before I added the top coat. Adding another 40lb bag of mix was going to make this harder to move.
Step 12: Top Coat
I really wanted the concrete to stick so I used bonding adhesive in the mortar mix. I mixed this 75% adhesive/25% water into the dry ingredients. After lightly misting the dry scratch coat, I applied the top coat using my gloved hands again. With the additive and the dry concrete looking for moisture, the top coat stuck really well, even on the undercuts and bottom of snout and torso.
Step 13: Waiting for Stain
I am letting the sculpture attain a semi cured point (one week) before I add stain. In the past I added watered down acrylic paint instead of keeping it damp with water. Seemed to work fine. This time, since I have a concrete arch that I built as well, I am going to give the acid stains a shot.
Step 14: Material and Equipment Required
This project used:
One large cardboard box free
1 roll masking tape $2
1 small roll fiberglass tape $5
3 bags 40lb. mortar mix $15
1/4 bag fiberglass fiber $5
1 5 gallon bucket $3
4 pairs of latex gloves $4
1/2 gallon bonding adhesive $10
1 Sharpie marker $1
TOTAL PROJECT COST: $45