Hi everyone!

 Well, the time has finally come when we get to legitimately talk about two great things, cuvettes and beer!  And, we’re not talking about Beer’s law, we’re talking about straight up brewski beer.

 Let the beer jokes commence!

 “Where do monkeys go to grab a beer? The monkey bars!“

What is SRM Beer AKA Beer SRM

 Ok so let’s get into this.

 For beer applications, SRM stands for Standard Reference Method, which if someone was drunk, with beer of course, they might confuse it with Standard Reference Materials which has to do with calibration standards. 

 SRM is one method used to help brewers classify a color of beer.  There is an endless array of beer colors.  The range spans from light yellow all the way to a dark black color.  There is an SRM number scale that ranges from 1-40+, check out the picture below to see the scale.

 Surprisingly they use spectrophotometers and cuvettes to do this.  Originally this was done with color slides which is known as the Lovibond system.  SRM is the more modern system that has replaced the Lovibond system that was created in 1883.  Brewers still use the term Degrees Lovibond when talking about colors.

 Here is how it works:  

 The attenuation of light must be measured at a wavelength of 430 nm.  So set your spectrophotometer for 430 nm and zero the machine.

A standard 10 mm (1 cm) cuvette filled with beer is placed in the spectrophotometer.  You only need 3.5 mL of beer, so we’ll leave it up to you to decide what to do with the rest of it.

 For SRM beer you have to scale the absorption by a constant which is 12.7.

 Here is the formula:

  “D” is dilution and “A” is the absorbance at 430 nm for the 10 mm cuvette.

 To convert SRM to European Brewin Convention (EBC) you can use this formula:

 EBC = 1.97 * SRM

 In other words, EBC color is about double SRM.

 “Give a man a fish and he will eat for a day. Teach him how to fish, and he will sit in a boat and drink beer all day.“

Cuvettes for SRM Beer Experiments

 There are many cuvettes that have a 10 mm lightpath that can used for SRM Beer.  But since we are only working at 430nm, we don’t need to go crazy and get a high end quartz cuvette. 

 The following materials will all work at 430nm:

•  Polystyrene (Plastic)
• Acrylic (Plastic)
• Optical Glass (Glass)
• UV Quartz (Glass)

The material you choose will depend on how much accuracy you require.  Quartz and glass cuvettes have much tighter lightpath tolerances than plastic cuvettes.  Tighter tolerances means better results, but it also means paying a higher price.

Plastic cuvettes are meant to be used one time and thrown out saving you the time of washing them out after each run.  The tolerances vary quite a bit from cuvette to cuvette so this should be taken into account.

We work with many companies that do color measurements for printers, beer srm, paints, coatings, plastics, malts and over various applications.  We find that these professional companies prefer to use optical glass.  Optical glass gives you the best balance of accuracy and price.

Running an SRM Beer/Beer SRM Experiment

What fun is it if we didn’t run our own SRM beer experiment.  So we grabbed a bottle of beer sitting in the fridge and gave it a run.  Let’s see where it stands.

Materials we used:

• 1- bottle Mystery Beer
• 1- UV/VIS spectrophotometer
• 1- 10 mm quartz cuvette (1UV10)

Step 1: Warm up spectrophotometer for 20 minutes

Step 2:  Fill up clean 10 mm cuvette with beer sample

Step 2: Set the spectrophotometer to 430 nm

Step 3:  Zero the spectrophotometer

Step 4: Insert cuvette filled with beer into the machine

Step 5:  Take the reading

Calculating SRM beer:

SRM= 12.7 x 1 (for no dilution) x 0.794 (our value at 430 nm)

So we get a rounded value of 10, putting our mystery beer in English Bitter category.

We’ve taken the time to write out this poem about cuvettes and SRM beer:

A Cuvette Full of Beer

When you want to drink about 3.5 mL, what can help

a cuvette full of beer.

When you want to relax in the lab but don't want to be fired, what can help

a cuvette full of beer.

When you want to feel like an American and a lab nerd at the same time, what can help

a cuvette full of beer.

When you need to vote for a crazy president, what can help

a cuvette full of beer. (lots of them!)

When rednecks invade your lab, what can help

a cuvette full of beer.

Until next time everyone,

The FyrfliSy Team