Sand baths have been used in labs since the time of alchemists. Simply, a sand bath is made by placing a container on a heated surface and filling with sand. A vessel to be heated is then submerged into the sand which conducts the heat from the heated surface into the sides of the vessel. In modern labs, sand baths are still used and are typically set up using a hotplate or heating mantle on to which a metal container of sand is placed.
How to make a sand bath
To make a simple sand bath set up, you will need:
- Hotplate with a metal top plate – you should not use a ceramic topped hotplate to make a sand bath. This is because the sand is held in a reflective metal container. The metal container reflects heat back into the ceramic plate and can cause it to overheat, brown and even crack.
- Metal container to hold your sand – there are specially designed sand bath containers out there, although this is not entirely necessary. All you need is a metal (most commonly used is steel) container of an appropriate size (smaller than the hotplate surface itself). Ensure it is high enough for your vessels to be adequately covered when sand is added.
- Heat proof vessel – choose borosilicate glass as this has greater temperature resistance
- Clean, dry sand
Sand baths have a number of advantages compared with simply using a hotplate. This includes:
- Heat is conducted directly into the sides of the heated vessel. Because of this the vessel is heated a lot more evenly than if the heat source was only coming from below
- Heating of vessels is more gradual so there is less risk of cracking glassware with dramatic temperature changes
- Heating is more even through the whole vessel so stirring is less necessary
- Should the vessel bubble over, the sand will catch the spillage and this can save your hotplate surface or lab bench from damage
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