Refractometer readings

[msppilot]

I got a new refractometer for Christmas and I am wondering about ho to read it. It has both the brix and SG scales. If I am looking for an O.G. of 1.065, will the refractometer read that after I am done mashing? How much does the O.G. change from the end of the mash to the time you take an O.G. reading before pitching the yeast?

 

[Clonefan94]

use the Brix scale and convert using math or an online calculator. From a lot of posts on here, it's tough to trust the SG scale. Also, double check it against a hydrometer, during a brew, just to make sure it's where it says it is. Yes, the refractometer will be able to tell you your gravity after mashing. Also after your boil. The math gets fuzzy though once you pitch the yeast, so I still stick to my hydrometer for FG readings.

The change in gravity, from the time you mash to the time you pitch yeast is mainly based on your boil off rate. This is different for every system. How much water you boil off, will determine the concentration of sugar in your post boil wort. Your refractometer will still read this fine though. It's actually the good thing about the refractometer, you can take the small samples during the boil, to find out how close you are getting to your target gravity.

 

[DRonco]

As you boil, you evaporate water. As a result, you concentrate the sugars in the liquid. This will be reflected in an increased gravity reading. As the beer ferments, the yeast will eat the sugars, causing the gravity reading to fall.

 

[FuzzBeckersHB]

I would say you could grab a sample right before pitching, that is the most accurate OG, post boil, starting volume. Just remember when checking for final gravity that you use a refractor conversion table, the alcohol in the solution will skew your reading when using a refractometer...also make sure you calibrate refractometer , and let your sample temperature adjust.....

 

[msppilot]

How about during the mash? If I am low during my mash I wanted to be able to add some DME to bring the O.G. up. The the reading be higher then the starting O.G. I am shooting for 1.065 O.G. How will I know if I should add DME based on the Brix scale?

 

[DRonco]

I believe the conversion is 4 to 1. ie: a sg of 1.065 = ~16 brix. (65/4). In general, 1 pound of dme in 1 gallon of water will give ~40 pg/g. So, that same pound of dme will add ~5 pg/g in 8 gallons pre boiled wort.

 

[BryceL]

How about during the mash? If I am low during my mash I wanted to be able to add some DME to bring the O.G. up. The the reading be higher then the starting O.G. I am shooting for 1.065 O.G. How will I know if I should add DME based on the Brix scale?

I think the measurement you are going to want to take is the pre-boil gravity. Whatever recipe or software you are using should give you the estimated pre-boil volume and gravity. This is after you sparge and all the runnings are in your boil kettle and you are at the proper pre-boil volume. You can then take a refractometer reading (in SG) and then add water or DME depending on if you are high or low. I use beersmith, but there should be some calculators online.

The other option, rather than adding DME is to boil longer. With a refractometer, you can account for this and not add your 60 minute hops until you have boiled off the amount needed to get your gravity to where it should be.