refractometer and gravity

[walker111]

Brewing a Rushmore IPA double batch later today and this beer turns out great . I am using a refractometer for the first time but will have my old standby hydrometer on hand.

I know my OG and FG but will test samples at mash, preboil, etc.
OG calls for 1.059 and I usually am 2 points over or under from past brews of this beer.

Question?
What number should I look for in my gravity readings prior to OG? Some recipes give this number and some do not. I know there are many variables. I fly sparge for an hour .......... I know ...... a long time, and I collect 13.5 g for the 15 g kettle.

First runnings are high gravities and I usually sparge until I get my volume required but trying to lock this in more accurate.

Also, first time brewing with my own crushed grains! Bought a barley crusher a month ago and a wide variety of malts. Had the BC on the factory setting but found the crush was too much so opened it up some and it appears good. Time will tell.
Thanks

 

[BrewingAroundtheRrealm]

The short version is to take your refractometer reading and multiply by 4.

There are several calculators out there. https://www.brewersfriend.com/brix-converter/ That one has the formula at the bottom for calculating it yourself.

 

[Calder]

The short version is to take your refractometer reading and multiply by 4.

This starts to vary once you get above about 11 Brix. The higher the gravity, the more the error with this simple calculation. You can find the relationship on-line.

FG (after fermentation), the refractometer reading is nowhere near the real gravity. the alcohol throws it off. Fortunately there are on-line calculators that can provide estimates for converting refractometer readings to SG.