Evaporating Dishes & Basins

Choose a dish that leaves the liquid filling no more than half its depth, giving enough spare surface area for fast evaporation without risking a boil-over. For routine classroom crystallisation, a mid-sized dish covers most tasks, with a larger basin kept on hand for bulk solvent evaporation.

For simple aqueous solutions, a wire gauze over a tripod and Bunsen burner gives fast, direct evaporation. For heat-sensitive compounds or flammable solvents, a water bath provides gentler, safer, and more controlled heating without exceeding 100°C.

Most evaporating dishes have a small moulded spout on the rim, which makes transferring the concentrated liquid or dried residue into another vessel far cleaner than tipping from a plain rim. Always check this feature is present if the next step in your procedure involves pouring the contents.

Always use tongs to move a hot evaporating dish, never bare hands, and let it cool on a heatproof mat before weighing or handling further. For gravimetric work, cool the dish in a desiccator to keep it dry and prevent it from reabsorbing atmospheric moisture before the final mass reading.

An evaporating dish is deeper with sloped sides and a pouring lip, designed to handle direct heat from a flame or hot plate. A crystallising dish is shallower with straight sides and thinner glass or ceramic, meant for slow, unheated evaporation and crystal growth over hours or days. Both work for crystallisation, but only the evaporating dish is rated for direct heating.

Yes, provided it rests on a wire gauze over a tripod stand rather than sitting directly in the flame. The gauze spreads the heat evenly across the base, reducing thermal stress on the porcelain and preventing the kind of localised hot spot that can cause cracking.

Glazed porcelain evaporating dishes resist most dilute laboratory acids and alkalis well. Avoid prolonged contact with concentrated hydrofluoric acid, which etches ceramic surfaces, and avoid sudden temperature changes, which can crack the glaze even on an acid-resistant dish.

Uneven crystals usually mean evaporation happened too fast, which favours many small crystals over fewer large ones. For larger, well-formed crystals, evaporate slowly at room temperature or on a very low heat, and avoid disturbing the dish once crystals begin to form on the surface or sides.

Once fully cooled, most residues dissolve with warm water; stubborn crystallised deposits can be gently reheated with a small amount of water or dilute acid to redissolve. Avoid abrasive scouring pads on the glazed exterior, and never plunge a hot dish into cold water as the thermal shock can crack it.