Heat preservation: Which material helps keeping temperature

Temperature plays an important role in brewing; it directly affects extraction. And material of dripper is one of the decisive factors of temperature in brewing. Everyone has their own choice of the best heat preserving material, but copper, plastic and ceramic are the three that people mention the most. On this post I want to share some of my opinions.

Before we started, there are two terms that we need to know:

Thermal Conductivity

Materials with higher thermal conductivity means it rise and lose temperature faster.

Specific Heat Capacity

If two materials under the same weight, material with higher specific heat capacity means it can absorb more heat and also release more heat. Also, material with higher weight will absorb more heat.

Copper dripper: Highest thermal conductivity, Lowest specific heat capacity, Medium weight

Copper has the lowest specific heat capacity among three materials and relatively light weight. Sounds like a good material for keeping temperature. However, its thermal conductivity is much higher than other two materials, which means it absorbs heat from hot water then pass heat to air very fast. With this characteristic, copper dripper is very suitable for fast brew methods (non-stop pour) and people who don’t like to pre heat their dripper.

(Photo from Hario website)

Plastic dripper: Lowest thermal conductivity, Highest specific heat capacity, Lowest weight

Even though plastic has the highest specific heat capacity of the three, but plastic dripper is very light weight, meaning it won’t absorb lots of heat from hot water during the brew (of course it won’t release heat neither). And it transfers heat to the air slowly, so plastic dripper has a very good overall heat preserving performance in brewing.

Ceramic dripper: Medium thermal conductivity, Medium specific heat capacity, Highest weight

If we only look at the indexes above, we might think ceramic dripper has a bad performance on heat preservation. But actually, ceramic’s thermal conductivity is only a little higher than plastic, meaning ceramic also lose temperature in a slower speed. Although ceramic (material itself) has lower specific heat capacity than plastic, “ceramic dripper” is much heavier than copper and plastic dripper. So in actual brewing, ceramic dripper will absorb more heat from hot water at the beginning, then during the late stage, ceramic dripper will start to release heat to keep the temperature for a longer time. In other word, ceramic has better heat preserving performance when we pre heat it, and in slow brew, long time brew methods (pour-pause and traditional dripping method).

Each material has its own characteristic, the material that best fits your brew style is the one that has the best performance for you.