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ÀWỌN OHUN WÍWỌ̀
Plaster of Paris from Gypsum
Gypsum is calcium sulfate with water locked in its crystals (CaSO4·2H2O). Heated to about 120–180 °C it gives up three quarters of that water as steam and becomes the hemihydrate, plaster of Paris. Mixed with water again it takes the water back and sets hard, starting about 10 minutes after mixing, warming as it sets and expanding slightly. The name comes from the big gypsum deposit at Montmartre in Paris.
Olùbẹ̀rẹ̀
Half a day
Ìlànà
1
1
Crush the gypsum
Crush the gypsum
With a dust mask on, break the gypsum in a sack with the sledgehammer and grind it fine in the mortar. Sieve it.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Gypsum (calcium sulfate)2 kgÀwọn irinṣẹ́ tí a nílò:
Àpò ọ̀gbọ̀ rẹ́gẹdẹ
Òòlù ńlá
Odó àti Ọmọ Odó
Ajọ Ojú Kékeré
Ìbòjú Eruku
Gíláàsì ààbò2
2
Weigh it
Weigh it
Weigh the powder and spread it thinly on baking sheets.
Àwọn irinṣẹ́ tí a nílò:
Òṣùwọ̀n Díjítà Ilé Ìdáná
Àwo ìdáná3
3
Calcine
Calcine
Heat it in the oven at about 150 °C, checked with an oven thermometer, stirring now and then. Steam comes off; carry on until a cold glass held over it no longer mists.
Àwọn irinṣẹ́ tí a nílò:
Ààrò
Ìwọ̀n Ooru Ààrò
Ìṣètò ṣíbí igi
Ìbọ̀wọ́ Tí Ń Fara Da Ooru4
4
How much weight it should lose
How much weight it should lose
Ń ṣí ìwé Jupyter…
5
5
Weigh again
Weigh again
Weigh the cooled powder. Turning the dihydrate into the hemihydrate loses about 16 % of the weight; much less means it needs longer.
Àwọn irinṣẹ́ tí a nílò:
Òṣùwọ̀n Díjítà Ilé Ìdáná6
6
Test a pat
Test a pat
Stir a spoonful into a little water in a bowl to a cream and time how long it takes to set hard. Feel it warm up as it sets.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Omi0.05 lítàÀwọn irinṣẹ́ tí a nílò:
Abọ́
Aago Ìdúró7
7
Store airtight
Store airtight
Seal the rest in an airtight container: damp air spoils it slowly.
Àwọn irinṣẹ́ tí a nílò:
Ohun ìkó tí afẹ́fẹ́ kò lè wọ̀Àwọn irinṣẹ́ tó nílò
15- Àyè
- Àyè
- Àyè
- Àyè
- Àyè
- Àyè
- Àyè
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