Pouring plaster into your impression mould is something I have been busy doing all week so I thought I'd pass on a few helpful hints while I'm still in 'casting mode'!
The first thing to remember is this is not an exact science. Many professional sculptors & craftsmen never measure quantities of plaster & water & rely on experience to get the mix they want. It doesn't matter if you add slightly too much powder/water when mixing your casting mix - it should still work out ok. What may vary is the amount of time you have before the mix sets & how strong the final piece is.
Secondly, plaster sets quicker the older it is. If you have a kit which has not been used within 6 months of purchase the plaster is likely to set quicker than stated in the instructions, giving you less working time!
Now for some real advice:
Plaster types: there are many & they vary in coarseness of the powder, hardness & setting time. Our kits use a plaster with a total working time of 5/6 minutes at room temperature. It is a form of dental plaster that gives excellent detail & good hardness whilst not being too hard to carve & sand once dry. There are many other plasters available & if using them you should obtain a data sheet with mixing ratios & setting times & experiment before pouring a mix into your precious baby foot mould!
Adding plaster to water: As a rule, you need 1 part water to 2 parts plaster. You should always add the water to the plaster & not the other way round. Pour the plaster into the water & make a little mountain in the middle of the water. This should be left to soak up the water for 1-2 minutes before you start mixing. This allows the water to be absorbed by the plaster in a nice, even manner & you are less likely to get lumps.
Mixing techniques: Mix from the bottom of the container in smooth circles. You are trying to mix without putting bubbles into the mixture. Mix for a minute or so - the more you mix the faster & harder the plaster will set so don't overdo it! As soon as you have a mix which is smooth like single cream you're almost ready to pour.
Removing bubbles: they are your enemy as they will catch in fingers & toes leaving your cast digitless. Tap the tub of plaster on a hard surface to 'knock out' as many bubbles as possible before pouring into the mould. If pouring a foot, half fill & using the bristle end of a paintbrush, 'paint' around the inside of the mould into every toe & as much of the inside surface as possible. Tap the mould to dislodge any more bubbles & then top the mould right up.
If pouring a hand, fill the mould once, empty the plaster back into the tub & then refill slowly. Clamp a cloth over the open end of the mould & shake well, tipping the mould upside down & shaking it in all planes to give bubbles a chance to escape. Then, remove the cloth, top up the mould & leave to set.
Lots of words here I know but it's all good advice! I think I need a video of these tips - watch this space!!
1 comment:
That is really helpful info, thanks so much,cant wait 2 give my next 1 ago now, thanks again, karen x
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