These lovely Christmas decorations make a fun project if you like making moulds and, although these decorations are slip-cast, the mould can also be used to press form them if you prefer that technique

You will need:
Plaster and associated mould-making equipment: bucket, non-absorbent board, cottle boards, plaster clay for making the models, and newspaper for cleaning up.
Casting slip – porcelain makes the best Christmas decorations because it casts thinly and quickly and needs no colour decoration – unless you want to add it.

 

BIRDS

1

Decide on the shape and size of your decorations – here we’re making birds, but you can make any animal you choose. The key is not to make the shapes too complicated – fine details can easily be added at a later stage.

Draw out the shapes on foam sheeting so that you have them for future use, then transfer the outline to a non-absorbent board – repeating the second half as a mirror image of the first, as shown.

 

2

Fill the outlines with soft clay to form the typical, rounded shape of a bird.

The two halves must match as closely as possible in proportion.

 

3

Once you’ve formed the shapes accurately, smooth over the surface with a kidney to make sure there are no unplanned marks or undercuts.

 

4

When you’re happy with the finish, build a shallow cottle around the model – these can be boards or even thick slab sections of clay. The depth depends on the depth of the models – make the cottle 2-3cm deeper than the top of the model for best results.

Secure the cottles with coils of soft clay to prevent the plaster escaping when it’s cast.

 

5

Mix a suitable amount of plaster to fill the model and cast it following the method shown here.

TIP:  If you prepare several models you can use up all the plaster mixture instead of wasting it if you find you’ve mixed too much for one.

 

6

Remove the cottle when the plaster has set.

Surform the edges to round them off and remove any sharpness that could break away and contaminate the clay. Discard the shavings carefully to avoid cross-contamination of materials.

 

7

Carefully lift the mould off the board and surform the upper edge in the same way.

Lift out the clay models by pressing a lump of clay onto the surface, as shown – this will release the clay, which should then lift out quite easily. DO NOT dig into the clay with sharp tools because you could damage the plaster surface below.

 

 8

Finish off any other moulds you may have made in the same way, then put them all somewhere warm to dry out completely before using.

 

9

When the moulds have dried out, prepare your chosen casting slip by stirring it thoroughly until it flows freely. The more you stir it, the more fluid it will become, and it needs to be quite thin to pour well.

Decant the slip through a kitchen sieve – to remove any possible lumps – into a large jug.

With all your moulds at the ready, fill each section of bird as full as possible.

 

10

Time your casts according to the type of slip you are using – a guide to timing can be found here.

 

11

When the correct time for casting has been reached, pour the excess slip out of the mould and back into the slip bucket.

Hold the mould over the bucket until it has mostly stopped dripping, then transfer it to rest on wooden battens over a bowl, as shown.

If you’re careful you can stack several moulds to drain in this way – just make sure the slip surfaces don’t come into contact with the plaster of the adjacent mould.

You can lay the moulds flat when the slip has lost its glossy, wet sheen and the clay looks as though it’s shrinking away from the sides.

 

12

Remove the slip that covered the mould when the excess was poured out, with a firm plastic kidney. Take the opportunity to remove any spillage around the shapes in the same way.

Note – Unless you can think of a really creative use for the scraps cleaned from the plaster surface, they are best discarded.

You should now be able to remove the casts from the mould.

 

13

Decant a couple of spoonfuls of casting slip into a small container, and water it down to a very thin consistency for joining the sections together.

BE AWARE: you can’t join cast sections with slip unless it has been watered down.

 

14

Carefully score the edges of each half of the bird with a serrated kidney. This is a delicate task and requires a light touch.

 

 15

Apply the thinned-down slip to both surfaces to be joined, then close the sections together, pressing as firmly as the casts will allow.

 

16

Work over the joins with a rubber or plastic kidney to neaten them up and remove any burrs of slip that may be protruding.

TIP: Use a small block of wood to consolidate the joins on the underside of the bird. Roll the shape several times in a rocking action, to ensure a good outline.

 

17

Wipe over the join with a damp sponge until the seam is no longer visible but don’t saturate the clay. If it feels like it’s getting floppy, firm it up again with a quick blast from a hairdryer.

 

18

Using a pen top or similar tool, impress the eyes into the head of the bird. The clay should still be moist enough to do this easily.

 

19

This is an optional extra and needn’t be done if you’re happy with your decoration as it is, but for those who would like more definition in the form, draw in extra details with a pin first to get the shaping correct.

Once the outline is in place, carve out the lines with a fine ribbon tool for stronger feature definition.

 

20

Wipe over the carved detail with a damp sponge to soften the edges a little.

 

21

Make the position to hang the bird from with a pin – pushing it carefully through the wall of the bird at the upper edge and through to the other side.

Now, enlarge the hole with a fine drill bit. It should be large enough to thread a ribbon through when fired.

Wipe over the drilled hole with a damp sponge to remove any burrs of clay.

 

 22

TIP:  Dimpled foam is great for supporting delicate items as they dry.

Allow the bird to dry out completely before bisque firing. If you want to, you can colour the bird using underglazes before glaze firing or if you’re using porcelain and don’t want to add any colour, simply fire the shapes right up to their final temperature.

Porcelain forms are best supported on a bed of alumina to help keep the shape when firing.

 

Thread your decorations with coloured ribbon and contrasting coloured beads for lovely Christmassy effect.

 

HEARTS

This is a variation on the birds – again using a plaster mould and slip casting but introducing an extra decorative detail.  You could easily adapt this technique to other shapes, like stars or baubles

You will need:
A heart-shaped two-part mould – make the mould in the same way as for the birds.
Sticky backed foam shapes – search pound shops for lots of choices at very low cost.  Alternatively, craft and hobby shops will have a good selection of Christmas shapes – snowflakes are good!

 

1

Having made your mould and dried it out completely, stick a shape into the centre of each half of the heart, making sure, as far as possible, that the shapes will be opposite one another when the heart is constructed.

Make sure the shapes are properly stuck down and won’t move when the slip is poured over them.

 

2

Prepare your casting slip as you did for the earlier decoration – stirring well until really fluid then decanting through a sieve into a jug.

Fill each half of the mould as full as possible, pouring directly over the central shapes first to ensure no air bubbles are trapped around them.

 

 3

Time the casting according to the type of slip you are using, then, when ready pour the excess slip back out into the bucket.

You will see the central shape in slight relief as you pour out the excess.

Allow the mould to drain over a bowl until the slip loses its sheen and starts to shrink away from the edges then remove the excess slip on the mould left behind from pouring out the excess, as you did for the birds.

 

 

4

Join the two halves together with thinned-down slip, making sure the seal around the edges is good.  Neaten up the joins with a kidney then wipe them over with a damp sponge.

Now, very carefully cut away the clay within the decorative shape.  The clay will be very thin and this is a delicate job which is most easily done with a pin.

Repeat the exercise on the opposite side so that you can see through the heart when finished.

 

 5

Neaten up the cutout shapes by brushing away the burrs of clay with a soft brush.

 

6

Make a hole to hang the decoration with a fine drill bit but make sure it’s large enough to thread a ribbon through.

Wipe over the holes with a damp sponge to complete the decoration – then allow it to dry before firing to your chosen temperature.

When fired, thread with a pretty ribbon and a bead to complete.

 

These projects first appeared in issue 9.

For more projects, click here

 

 

 

 

 

 

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