[bruck]

HI folks....Got a refractometer with ATC for x-mas and was pretty excited to start using it. I have used it a couple times and the readings just don't seem right when compared to my hydrometer. I am converting the Brix back to OG using Beersmith software and it keeps coming out lower then my hydrometer readings. Both have been calibrated so I can't figure out where the gap is. Is the hydrometer more accurate or vice versa? Thoughts and thanks!

[Kaiser]

I'm surprised nobody has chimed in yet.

1) refractometers can only measure the sugar content of wort properly. Once there is alcohol in the sample you need to use a conversion formula that takes the current alcohol content (calculated from the OG of the initial wort) into account. There are a number of calculators out there

2) refractometers are calibrated for sucrose solutions which refract slightly different than brewer's wort. As a result even your brix reading from wort needs to be corrected. The error is fairly small, though. Many brewers cite a correction factor of ~1.04.

There have been a number of posts and articles about using refractometers. Here is a good one from byo.com: http://www.byo.com/stories/projects-and-equipment/article/indices/29-equipment/1343-refractometers

Kai

[bluesman]

You beat me to it Kai! 

I use a refractometer regularly when mashing and boiling. Evaporation is a key concern when sampling. I use a dropper and sample quickly. Clean your dropper with distilled water and ensure it is dry upon each use. Apply several drops to the plate and cover. Allow 15 seconds for the tempeature to equilibrate.

Make sure you calibrate your refractometer with distilled water prior to use to ensure proper calibration. I usually take multiple readings to ensure repeatability. Assure that there are no visible solids or bubbles on the daylight plate.

Always clean the plate with warm water and dry with a clean soft cloth after each use.

A refractometer is a great way to qualify and confirm your mash is converting as well as determining the amount of sugar that is in your wort. I won't brew withoout it. 

[Thirsty_Monk]

A refractometer is a great way to qualify and confirm your mash is converting

Could you elaborate on this one?

Thank you

[Kaiser]

I think he is talking about this:

http://braukaiser.com/wiki/index.php?title=Troubleshooting_Brewhouse_Efficiency#Determining_Conversion_Efficiency

As starch is converted it increases the gravity of the sweet wort in the mash. There is a limit to that gravity which depends on the extract potential and the current mash thickness.

Plotting this for a few batches is the driving force for me to finally get a refractometer. But I always end up finding something that I need more urgently.

Kai

[bluesman]

A refractometer is a great way to qualify and confirm your mash is converting

Could you elaborate on this one?

Thank you

As Kai has shown...

Starch conversion occurs through enzyme activity in your malted grains. Your goal is to get 100% starch conversion from your mash, which may be hindered by several variables (crush, temp, time etc...) Most single infusion mashes are run for 60 minutes, but you'll see some recipes calling for 45 minutes and some calling for 90 minutes. Which is right?

An iodine test will tell you if you've converted, but a refractometer will quantify the conversion. As the starch is converted into sugar, the sugar in solution is increasing which can be measured by a refractometer.

[bruck]

Very helpful folks. I will read up on the BYO link provided. I really want to make good use of this thing, but definately am doing something wrong. Thank you.