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CRYSTACAL ALPHA K x 25kg

Crystacal Alpha K

Product Code: 4035/25
Size: 25kg
Stock: Temporarily out of stock
Price: £47.20

Quantity: 

Mixing Ratio: 100-21 (5lb 15oz. per pint or 4.76kg per litre)
Vicat setting time: 20-35 minutes.

Pack: 25kg
Hazard Symbol: NONE


A super hard, low expansion plaster where maximum strength and surface hardness are required.

MIXING


Weighed quantities should always be used. The bulk density of plaster is variable and so measurement by volume is not reliable. Records should be kept of the plaster water ratio used in each type of cast so that mixes can be adjusted accordingly.

Use clean water only. It should be as pure as possible. Usually if water is drinkable, it is suitable for mixing plaster. For consistent results, a constant water temperature should be maintained. Ideally, this should be in the range 16-20°C (61-68°F)

Ensure all containers and tools are clean and free from set plaster. Do not mix fresh material with plaster that has been mixed some time previously.

HAND MIXING


1. Weigh the plaster and water accurately for each mix.

2. Sift or strew the plaster into the water slowly and evenly. Do not drop handfuls of plaster into the water. Always add the plaster to the water, never the reverse.

3. Allow the plaster to soak for at least one or two minutes. This soaking period removes air and allows each gypsum particle to be saturated with water so that it is easily dispersed during mixing. While waiting, the sides of the container can be tapped to bring air bubbles to the surface.

4. Mix as required by stirring. This is best done by placing an outspread hand into the bottom of the container and stir. Keep the stirring action below the surface of the water so as not to entrap any additional air. Move the hand from the bottom to the top breaking up any lumps encountered. Skim off any air bubbles or scum that may have risen to the surface. Mixing will take 2 to 5 minutes, depending upon the type of plaster being used, the plaster water ration and the quantity being mixed.

5. Gradually, the mix will change consistency and begin to take on a creamy, uniform texture; at this point it is ready to pour.

6. Pour lifting the mix carefully over the mould and gently pour in a thin continuous stream in one spot, letting the plaster flow freely up and around the inside of the mould until it crests just above the lip of the mould. Tap the sides and shake the mould to release air bubbles that will rise to the top.

7. After the mould or moulds have been filled, pour the excess plaster remaining in the mixing container into a waste bin and clean the mixing bowl and any tools used. When the plaster has begun to set, remove the excess plaster on the mould by scraping the plaster flush with the lips of the case mould.
 

MECHANICAL MIXING


1. Weigh the plaster and water accurately for each mix.

2. Sift or strew the plaster into the water slowly and evenly. Do not drop handfuls of plaster into the water. Always add the plaster to the water, never the reverse.

3. Allow the plaster to soak for at least one or two minutes. This soaking period removes air and allows each gypsum particle to be saturated with water so that it is easily dispersed during mixing. While waiting, the sides of the container can be tapped to bring air bubbles to the surface.

4. Use a mechancial mixer and mixing bucket of an appropriate size and design. Mechanical mixing considerably reduces the required mixing time. The time taken will depend upon the type of plaster used, the plaster water ratio, the volume of the mix as well as the type of mixer used.

5. As a general guide, direct drive propeller mixers are the best. The propeller should clear the bottom of the contaienr by 25-50mm (1 to 2 inches) and the shaft should be about half way between the centre and side of the mixing container. Mixer speed should not exceed 450rpm; a variable speed control can be of assistance. The propeller should force the mix downwards, but not form a vortex, which will induce air into the mix. All equipment must be kept clean to avoid causing accelerated set of the plaster mix.

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