Here are a couple of sprig options we’ve previously covered

Disregard the theme of each sprig (unless they happen to be topical – that depends on when you’re reading this!),  the method is the same for whatever shape you want to make. If you’d like to see the projects we’ve used these in, the first one is in issue 9  and can be found online  here and the second is from issue 13

Hollow sprig

These lovely decorations make a fun project if you like making moulds and, although these birds are slip-cast, the mould can also be used to press form the birds 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 tree decorations because it casts thinly and quickly and needs no colour decoration – unless you want to add it

 

 1 

design for hollow sprig

Decide on the shape and size of your decorations – here we’re making birds, but you can make anthing you like. 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.

 

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

 

preparing to cast hollow sprig

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.

 

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.

 

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 

releasing sprig from mould

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.

 

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.

 

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 

drying sprig double sided

Time your casts according to the type of slip you are using – a guide to timing was given in issue 8, and can also 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

removing excess slip from sprig mould

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 

This is where you can stop if you’re making single-sided sprigs for surface decoration. Jump to step 22.

If you want to make a double-sided form, we’ve left the remaining instructions here.

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 

fettling sprig ready for joining

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 

joining two sprig halves together

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

sprig fettling

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 

sprig bird details

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 

sprig bird hanging holes

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.

 

Solid sprig

Here,  you’ll learn how to make moulds from models made to your own designs

You will need:
A non-absorbent board or glazed tile
Drawing or picture of your design (outline template in card is optional)
Fine marker pen
Smooth soft clay to make the model from
Plaster
Bowl or jug to mix the plaster in

 

outline sprig design

Transfer the outline of your design to the surface of your tile, either freehand or by drawing around the template with a fine marker pen.

 

 2 

filling sprig outline with clay

Start to fill in the outline with clay. Carefully fill in up to the marked line taking care to angle the clay inwards at the edges to avoid undercuts.

Sprigs are traditionally thin, but build up the surface to about 5mm thick to begin with, so that you can model detail into the surface later.

 

smoothing clay sprig

Smooth over the model periodically with a rib as you form the basic shape – it helps to stay in control of the sprig from the onset.

 

removing any undercuts on sprig

Mitre the edges carefully with a wooden tool to ensure there are no undercuts that could trap plaster and spoil the sprig.

 

 5

sprig mould smoothing

When you have the basic shape in place with no undercuts around the edges, smooth over the surface with a rubber kidney or your finger.

 

adding texture to sprig model

Now draw lines into the shape with the tip of a tool or pin to define where you will carve out the detail. This detail will ultimately give some visual movement to the shape.

 

Use a wooden modelling tool or loop tool to carve into the clay between the drawn lines. Remove any excess clay as necessary and possibly build it up in other areas if required. Be mindful of creating undercuts as you work, and correct any areas you think may be a problem.

 

Smooth over the surface of the model with your finger carefully.

The model should now be ready to cast in plaster.

 

 9 

building cottle for sprig moulding

Build a shallow cottle around the model with a thick slab of clay – securing it in place with a coil on the outer wall.

TIP: because the amount of plaster required to make moulds like this is very small, it is useful to make several models at once so that if there’s plaster mixture left over it won’t go to waste.

 

Make one or two more models for casting.

 

10 

pouring plaster into sprig mould

Mix enough plaster to cover your models, allowing a depth of about 3cm for each.

Use the guideline of 1/12lb of plaster (675g) to 1 pint of water (575ml) and scale the amount up or down accordingly. A one-pint mixture will easily make two or three moulds, depending on their size, and is a good amount to mix.

Make sure you cover the model with plaster first, in case you don’t have enough mixture to fill the cottle.

 

11 

Lift the board and tap it on the work surface several times to bring any trapped bubbles to the surface.

Allow the plaster to set.

 

12

surforming sprig mould

Remove the cottle from around the mould when the plaster has set, then surform the edges to remove any sharp areas of plaster that could otherwise break off and contaminate your clay.

Dispose of the shaved off plaster carefully – wrap it in newspaper before putting it in the bin.

 

13 

removing master model from sprig mould sprig mould finishing edges

Separate the mould from the tile or board carefully, then surform the edges again to remove sharp bits of plaster.

Remove the clay model from the mould and discard the clay (it can go into a bag of clay used only for plaster mould-making). Wipe out the interior of the mould with a damp cloth then put it somewhere to dry out.

Small moulds like these will dry in a matter of days if kept somewhere warm.

 

sprig mould final

Your mould is now ready to use.