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 (updated with stainless steel and glass on 2023). 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.

Highest to lowest: Copper > Stainless Steel > Ceramic≈Glass > Plastic

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.

Highest to lowest (at the same weight): Plastic > Ceramic≈Glass > Stainless Steel > Copper

Copper dripper:

Copper has the lowest specific heat capacity among five 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.

Stainless Steel dripper:

Stainless steel has a litter higher specific heat capacity and much lower thermal conductivity compares to copper. And the weight of stainless steel drippers are usually similar to copper drippers, so it doesn't absorb much heat but it also won't keep heat for long. If you looking for your brew temperature going down by time linearly, then you might want to try stainless steel dripper.

(Photo from Hario website)

Plastic dripper:

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.

Glass dripper:

Very similar thermal conductivity and specific heat capacity data as ceramic; however, glass drippers have much lighter weight compare to ceramic drippers (still heavier than plastic and stainless steel/copper though). Which make glass drippers will not pass the heat out fast and can still keep some heat for a longer brew. Glass dripper is a pretty balanced choice no matter what brewing style you are using. And for few drippers that use double wall glass, I think they have the best performance for preventing the heat runs out.

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.