## Percolation

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# P 1.01 – Preheating

## Preheating

Filter cones are fabricated from a range of materials — most commonly, plastic, ceramic, metal, and glass. When preparing your filter cone at the start of the brewing process, the vast majority of the heat loss in a filter cone occurs at the air-water interface. All drip coffee methods feature a wide opening at the top exposed to the air, which means they are prone to losing energy. Before you commence your brewing process, you must ensure that your brewing device won’t deprive your brew water of the energy it needs to extract the coffee properly.

### Heat Loss – Specific Heat

It makes a surprisingly big difference to your brew water temperature if you preheat a filter cone. To help you ascertain how much energy your equipment has the potential to absorb out of your brew water, we have designed a new temperature equilibrium calculator. We will provide a few details to help you understand how this calculator works.

A filter cone made of a material with a higher specific heat (cp) will absorb more of the energy in the water. The specific heat is the amount of energy it takes to raise the temperature of a kilogram of a material by 1° C. The following table shows you the specific heat of a range of common substances used to fabricate filter cones. The energy is measured in units called Joules (J).

 Material Specific Heat J/Kg/°C Ceramic 1085 Glass 753 Perspex / Acrylic 1250 Stainless Steel 490

Source: engineeringtoolbox.com

Note: In physics, the rate at which an amount of energy is consumed is called power, and power is measured in watts. It takes 1 watt of power to produce 1 joule of energy per second.