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HOW TO DO IT SECTION
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MEASURE THE WATER The first step is to measure the amount of water you well need fill the mould with water to just below its rim Tip the water into the mixing bowl This leaves the mould damp which is what you need to make the plaster mixture work its way into every nook and cranny of the mould. Also, this gives you an easy way to work out the size (if the hole in the support you
MAKING A SUPPORT Simply roll back the rim of the mould A (everyone has a rim) and let the edge of the inside of the damp mould. Mark a piece of cardboard B . Cut a hole in the cardboard the same size and shape - the mould sits in the hole with its extra rim or collar supporting it C.
With Smaller Moulds like chess sets, all you need to do is suspend the mould by the cardboard in a jam jar or over the bowl. Larger moulds may need more support - strips of wood under the cardboard or even thin plywood. To give you an idea of size, a bucket makes a good container for a mould the size of a Gnome. |
PLASTER
ADDING THE POWDER. Always
add the powder to the water and not the other way round. Gently
spread the powder over the water until all the water is absorbed. No
measurements are necessary
but you will need about 1 1/2 times more powder than water. Leave
for 20 seconds to allow all the water to be absorbed, then stir
gently Fig 1
FILLING
THE MOULD
Spoon
the Mixture into the mould until it is
GETTING
RID OF THE AIR
Gently
flex the mould to work the mixture into all Those areas of fine
detail such as faces, ears, hands and feet, and any patterns -
if you don't you will have pinholes in the cast and possibly it will
lose some important details when it sets Fig 3.
PLACING
THE MOULD IN THE SUPPORT Leave until the casting is quite hard (about 40 minutes). To check run year finger nail across the costing - it should feel firm and dry Fig. 5
SOAPING
THE MOULD When the casting is hard, cover the outside of the mould thoroughly with a soapy water solution (or washing up liquid), and peal the mould back slightly from the base fig 6.
REMOVING
THE MOULD
Pull
firmly and as quickly as possible BUT FOLLOW
the
way the figure goes - don't pull against it or you will damage
it Fig .7 FINISHING Finish the cast off by trimming with a knife and levelling the base with a piece of sandpaper. Fill any small holes with plaster and dry thoroughly FIG. 8 |
LARGE MOULDS The important thing about large moulds is that they must be very well supported or the cast will become distorted. A double casting method is recommended except when you want to produce casts made with sand and cement 1. DOUBLE CASTING Make sure you use plenty of powder when double casting. 2. FILLING THE MOULD Fill the mould about 1/3 full of water, pour into a mixing bowl and add moulding powder until creamy flowing mixture is obtained. 4. POURING THE MIXTURE Pour the mixture into the mould (which must be damp). Flex the lower half of the mould to reduce the air bubbles and squeeze the mould to force the the mixture upwards so coating the whole of the inside mould. Carefully rotate the mould at an angle of 45 degrees, this will cause the mixture to flow evenly over the coating. Continue rotating until flow ceases. 5. PLACING THE MOULD INTO A SUPPORT. Place the mould very carefully in the support and allow the mixture to set fully. Then fill the mould up with a freshly mixed batch of material (which you have measured in the usual way before you undertook steps 2 and 3 ). Care should be taken not to crack or damage the hardened coasting already formed on the inside of the mould when filling the second time. 6. SOAP THE MOULD Make sure the cast is completely set before taking the mould off. Soap the outside of the mould. 7.REMOVE THE MOULD Remove the mould and finish of the cast off. |
SAND & CEMENT As it is not possible to use double casting with a concrete mix, you must make sure the mould is well supported. TO SUPPORT THE MOULD AND CASTING Use either fiberglass jacket which will give you the perfect results and really professional finish or bury the mould upside down in a sand box. The sand should be damp so it stays in place but doesn't dent or distort the mould. Fibreglass jackets can be specially made to order - phone or write for further details. You should prepare the sand box, then pour about half the casting mix into the mould and squeeze the mould to push the mixture into every nook and cranny. Then pack the sand round the mould to the neck and continue filling.
THE MIXTURE Your local store will have stocks of sand and cement. Mix 2 parts sharp sand to one part fresh cement. Then add water and stir until a thick creamy mix results. It should be pourable - but not to watery (because then the concrete will crack). POUR into the prepared mould about 3/4 full. Squeeze to get rid of air bubbles, Stir with a clean stick to bring any trapped air to the surface. Then fill the rest of the mould and stir to remove air bubbles. LEAVE for 24 hours (2-3 days is necessary in the winter) Soap the outside of the mould and then PULL THE MOULD from the casting. |
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