Easy way to cut a glass bottle

Safe­ty pre­cau­tions

Per­form this ex­per­i­ment only un­der adult su­per­vi­sion.

Equip­ment

• glass bot­tle;
• cot­ton string;
• iso­propyl al­co­hol;
• deep con­tain­er with cold wa­ter;
• sand­pa­per.

Step-by-step in­struc­tions

Wind a cot­ton string around a glass bot­tle. Soak it with iso­propyl al­co­hol and set it on fire. Ro­tate the bot­tle so the glass heats even­ly. Then im­merse the bot­tle in cold wa­ter – it will crack where it was heat­ed. Sand the edges with wet sand­pa­per. Your glass is ready!

Pro­cess­ de­scrip­tion

The iso­propyl al­co­hol burns on the cot­ton string, re­leas­ing plen­ty of heat. The bot­tle must be kept hor­i­zon­tal and ro­tat­ed con­stant­ly so that it heats even­ly. Glass has poor ther­mal con­duc­tiv­i­ty and main­ly warms up ex­act­ly where it’s heat­ed. As the glass cools abrupt­ly, a tem­per­a­ture dif­fer­ence aris­es be­tween the out­er and in­ner lay­ers, and the ef­fect of ther­mal ex­pan­sion cre­ates ten­sion in­side the glass, crack­ing it.

Do you want more fun facts and in­ter­est­ing ex­per­i­ments? Sign up for a “MEL Chem­istry” sub­scrip­tion!