| Answer | Crossword Clue |
|---|---|
| HEATPUMPS | Alternatives to furnaces |
| GANISTER | Rock used to line furnaces |
| ganister | highly refractory, siliceous rock used to line furnaces |
| firebrick | A brick capable of withstanding intense heat, used esp. to line furnaces and fireplaces |
| firebricks | A brick capable of withstanding intense heat, used esp. to line furnaces and fireplaces |
| refractaries | REFRACTARY, a substance that is able to resist high temperatures, etc, used in lining furnaces, etc |
| refractary | (obsolete) refractory / a substance that is able to resist high temperatures, etc, used in lining furnaces, etc |
