Word of the Week - Turbidity

According to the all-knowing Wikipedia, Turbidity is the cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air and is considered a key test of water quality. Now that you know that, why should you care about Turbidity.

Well, Turbidity is a key to understanding the color measurement for your beer and why it is the color that it is. One way that beer color can be measured is by using a spectrophotometer to measure the absorbance of light at 430nm nanometers, as it passes through a sample. This method was established by the ASBC as a way of standardizing the color measurement process. At the time, it was measured against colored glass plates and was done manually which allowed for a degree of error. The 430nm of light bandwidth was selected at the time to create a set of results that were consistent with the Lovibond measurement that was used at the time. Thus, the Lovibond and the new Standard Reverence Model (SRM) were used interchangeably.

Turbidity makes its appearance as the cause of less light to pass through the solution, thus creating darker wort and a higher Lovibond/SRM scale rating. This explains why you can actually filter color out of your beer if you use a fine enough filter medium.

There are other ways of measuring the color as well. Many brewing suppliers sell charts that brewers can use to compare beer samples to and get a rough reading of their SRM/Lovibond measurement. I have included a table from http://en.wikipedia.org/wiki/Standard_Reference_Method that can be used in the same way and also shows where various styles fall on the scale.

Hope you enjoyed the word of the week.

Cheers!