Fruit and Vegetable Art - Silicone Moulds and Plaster Casts

This is a bit of a weird one, but if you've been to Brick Lane in London, you will understand. I visited this peculiar part of London a few years ago and a whole street was covered in real, spray painted broccoli mounted all over the place. It was a street installation started by a local artist in response to bizarre news trending all over British media. England had a massive shortage of broccoli at the time and it got weird for a while, people were panicking and broccoli was even rationed in supermarkets for a while. After broccoli crisis was solved, broccoli art was still a thing in Brick Lane, except this time, it was turned into plaster sculptures. I was in the middle of moving into a new house, so that gave me an idea for some unusual, quirky kitchen decorations. I made my own broccoli mould and cast several plaster vegetables to hand on a wall. They were ruined by accident few weeks ago, so here I am, showing you how to do it yourself.

Broccoli is a bit of a useless shape, can only be used to make a wall art, but there are plenty of veggies and fruits with interesting shapes and textures that can actually be useful. In this Instructables I made a pineapple shaped plant pot/ pen holder. Honeydew melon has a gorgeous texture and could be turned into a bowl, same goes for cauliflower and pumpkin. Durian fruit has a lovely exterior, but I admit, I was unable to make myself buy it, the smell was too much for me, much to my dismay.

Supplies

Wooden or melamine board
Small screws or nails
Spray paint or spray-on varnish to seal and prepare the broccoli
Silicone - I used RTV moulding rubber, that had to be mixed with a catalyst. It has a relatively low viscosity, perfect for pouring over objects, but not for brushing them, so I also had to purchase thixotropic additive.
Spray-on release agent
Plaster bandages, plaster and/or quick set cement mix
Disposable mixing cups, stirring sticks, brushes etc
Plasticine
Glue gun (optional)
Sanding pads, exacto knife
Acrylic paints or spray-on paints
Spray-on sealer

Step 1: Preparing Broccoli

Find the best looking side on your broccoli and cut it in half with a sharp knife. Brush any loose bits and get rid of leaves on the stem.

Find a large enough board to fit the broccoli and leave approximately 1-2 inches of space around it.

Trace the broccoli shape onto a board with a marker and mark where to put your nails or screws. You want the screws to push through the meaty parts of the vegetable, stem and middle of the head.

Spray paint the broccoli two or three times. Spray paint will get into these tiny crevices and glue all head buds together, so silicone doesn't just seep into the cracks. This is a special case with broccoli only, most veggies and fruits won't need this special treatment.

Step 2: Nail the Broccoli

You have one shot at this, so don't hesitate. Align the broccoli with the outline and impale it onto the screws. It has to stay in this position for at least 1 whole day.

Use plasticine (or air dry clay, super light clay, blutack) to fill in any gaps between the stem and the head, also, fill any holes between the board and the stem if necessary.

Use glue gun of plasticine to create a 1-2 inch border around the broccoli, it will prevent silicone from spilling over.

Step 3: First Silicone Brush On

I sprayed the broccoli and my board with a generous amount of release agent, paying extra attention to the head and the underside.

Silicone rubber I'm using has to be mixed with a catalyst, which activates the silicone and determines how long the silicone will be workable and how long the curing period will be.

I used 60g of silicone for this first layer and since it was a very quick job, I added enough additive to have a very short pot time and curing time (it set in 3 hours).

I applied the silicone with a disposable brush to every part of the broccoli, half of that slid off to the board, so don't worry, it's supposed to happen. I paid extra attention to the head, to make sure all tiny bits were covered.

I had a small amount of leftover silicone, about 15 ml, which I left in the cup and let it cure. Once cured, I extracted it and cut it up into small cubes to create keys.

Step 4: Second and Third Silicone Layer

Once first layer was set I mixed another pot of silicone (100g this time) and added thixotropic additive to thicken it. It went from the consistency of thick cream to the consistency of royal icing / whipped cream. I used a brush to lather it all over the broccoli. I went over all the details while pushing the silicone in and creating a thick layer. It took a bit longer to cure - 6 hours because I needed extended pot time.

Third silicone mix was just as thick as the second layer and I applied it with a spatula to thicken the mould and make it stronger. All the details were already covered in silicone, so it was a relatively quick job of just slathering the silicone on the broccoli. I also extended the silicone to 1-2 inches around the broccoli and pressed a few keys into the boarder. It will help with attaching the empty mould to the plaster casing. I forgot to take a picture of the third layer, but I marked where to press keys in the picture above.

If I had to do it again, I'd make sure to smooth the last layer of silicone as much as possible, because mine ended a bit of a mess, which isn't that much of a problem, just made it a bit difficult to apply plaster bandages.

Step 5: Plaster/Cement Casing

Once everything was set, I sprayed the silicone mould with a release agent and applied plaster bandages. Once they dried, I added a layer of plaster of Paris, I mixed it with a minimum amount of water to create a thick paste and applied it with a spatula.

When it dried and I was ready for a final layer, I run out of plaster, but I had a lot of quick set cement, so I used it instead. I layered enough cement to cover the mould, added a lot of cement to the stalk area to even it out to make sure the mould will be able to stand on its own.

Step 6: Removal of the Broccoli

I left the cement and plaster casing to dry for a few hours and then removed it from the board.

At that point my broccoli was out of the fridge for two days and wilted a lot, so I just picked it up from the board, it wasn't stuck to the nails anymore.

I removed the silicone part from the plaster casing and then removed the broccoli.

The mould was very clean on the inside, but there were few parts where silicone seeped into broccoli and I had to forcibly pull it out and then had to use small sharp scissors to even out the inside of the mould.

I gave it a good wash with a soap and scrubbed it with a nail brush to get rid of any organic matter.

I dried the mould with paper towels and popped the silicone mould back into it's cement casing.

Step 7: Plaster Casting

To create plaster casts just mix plaster and water and either pour it all the way to the top, or pour just 1/3 - 1/2 amount and swirl it around to create hollow, lighter cast. I used plaster of Paris and rapid cement to cast my broccoli and both worked great, the only difference was the weight (cement was heavier) and breakability (hollow plaster casts were more fragile than full plaster casts).

I didn't use any mould release, it wasn't necessary.

Step 8: Casting Removal

I needed a third hand while removing the plaster casts, but overall, it was easy to peel the silicone away from the cast. If set properly, plaster is very durable.

Step 9: Painting

Cement casts had to be painted white first, but after that first base colour, I was able to apply acrylic paints with ease. First layer of paint had to be watered down a little bit to make it thinner. I could apply thinned paint to the head and get all those tiny crevices painted.

It took about 2 hours to dry, but once first layer was dry, I applied second layer of regular paint. For some colours I had to apply a third layer, but that's down to the quality of the paint itself.

Step 10: Pineapple Preparations

For the pineapple the only thing I had to do was getting rid of these leafy parts that grow all over the fruit. I just cut them off with a sharp exacto knife.

I cut the top of the pineapple and evened the top to make it as level as possible.

I attached it to the board the same was as broccoli- screws, followed by a hot glue boarder, and then followed with a release agent spray and one layer of thin silicone applied with a brush.

Step 11: Pineapple- Silicone Layers and Plaster Casing

I applied second and third layer of thickened silicone rubber and let it cure. I also added keys (around the border) for easy mould reattachment.

I created two-part plaster casing for easier removal. I started by layering plaster bandages, followed by two layers of thick plaster mix to one half of the mould (pic 2). Once plaster was dry, I covered that first half of the casing with a cling film and applied a layer of plaster bandages to the second half of the mould, I made sure second layer overlapped the first layer. Make sure that first plaster half is covered by the cling film, if it slides, your plaster halves will just join together and your casing will be useless.

Apply thick plaster paste to the second half and let it dry.

Step 12: Pineapple- Mould Removal

Once dry, those two plaster casing halves will just pop off and you will be able to extract the pineapple without any problems. Use exacto knife to cut all the way through one or two sides of the silicone mould to extract the fruit without tearing the mould.

Wash the silicone mould and scrub it with a nail brush to get rid of any organic matter. Dry with kitchen towels and assemble the mould and plaster casing.

Step 13: Pineapple- Plaster Casting

Once the mould is assembled, fill 1/4-1/3 of the pineapple with plaster mix and swirl it around to create a pot. My plaster sets in 5 min, so I just had to swirl the mould for 2-3 min before plaster thickened enough not to slide to the bottom of the mould. Let it dry and repeat this process until your cast is thick enough for your liking.

I didn't care for the smooth interior, so instead of swirling my third layer of plaster, I just applied it with a spatula. Once it set, I gave it a rough sanding with a 40 grit sanding pad.