Expanded Perlite: Volcanic Glass Puffed in a Minute of Fierce Heat

Perlite is a volcanic glass with water locked inside. Heated fast into its softening range, the water turns to steam and puffs each grain up to 7–16 times its volume, brilliant white and light (Wikipedia). The U.S. Bureau of Mines (1946) found that grains up to ¼ inch need only 1 to 3 minutes at the right heat, somewhere between 1,600 and 2,600 °F depending on the ore. The picture: expanded perlite (photo by KENPEI, Wikimedia Commons, CC BY-SA 3.0).

متوسط

A few hours

التعليمات

Crush and size

Break the perlite ore into grains no bigger than ¼ inch and sieve out the large pieces.

المواد لهذه الخطوة:

خام البيرلايت1 كغ

الأدوات المطلوبة:

مطرقة يدوية

منخل خشن

Heat it fast

Heat the kiln first. Drop a thin layer of grains in on a hot dish for 1 to 3 minutes, then take them out. Slow heating does not work.

الأدوات المطلوبة:

فرن حراري

طبق ضحل

كمّاشة طويلة الذراعين

قفازات لحام

Find your ore's heat

Each ore has its own heat, between 1,600 and 2,600 °F. Too cool and it hardly puffs; hotter puffs it more. Too hot and it melts, lets the gas out, and shrinks back to dense slag. Test small lots first.

الأدوات المطلوبة:

فرن حراري

طبق ضحل

كمّاشة طويلة الذراعين