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Doctor's Orders Brewing
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I recently purchased a Refractometer for measuring the SG of the runoff when sparging. This is much easier as you only need a drop of liquid rather than cooling a small jar to then be able to measure SG with a hydrometer.
I have put together a quick sheet to convert Degrees Brix (what the refractometer takes readings in) to SG.
I've uploaded it here for anyone else who has a refractometer and is interested.


View attachment Brix2SG.pdf
I found that I needed more granularity in the conversion table.
So here is version 2 that gives just that.


PS: Looks good if you laminate it. Then it means you can get water and wort all over it and not ruin it while brewing. Luckily we have a laminator at work :)

View attachment Brix2SGv2.pdf
Looks great Doc, just printed it out :D

I should be bale to get those other conversion/php script up over the weekend
3 weeks max and i'll have my refractometer.
can't wait. As well as measuring the run off it will be great for measring the start boil gravity and end boil gravity, even half way though pretty much at any stage.
so i can really fine tune the final wort size and gravity in the kettle.
For the run off at the moment i just measure at sparge temp and add 1.010 for temp difference. then just cool a enough so it want melt the plastic tube to measure boiling wort which ends up being 70c after swishing in a glass so i just add the 1.010 again.
so you can do with out a refractometer but for under $100 it makes for a great brewing toy.
it seems unless you use either beersmith or promash. you really can't use a refractometer for fg. simply because the maths is to much for the average human brain. Mainly due to the difference in alcohol being present which causes the refraction of light not to be a correct measure of the level of sugar.

Doc do those tables take into account any wort calibration?
Anyway good work, i'll have to adjust mine to read 'Skunk Fart brewery'. with thanx to 'dr's orders'
The table is a straight conversion using the formula at the bottom of the chart.

I use it every time I brew to check my 1st, last and full wort gravities.

My post boil gravity I do with a hydrometer as it is also what I use at the end of fermentation. Consistency and non-reliability in the maths for the formulas of using a refractometer with wort with alcohol content is why I still use a hydrometer for those calcs.

But using the refractometer for measuring runoff is fantastic.

I've been getting a few queries about my refractometer, so I have resurrected this thread.

I bought mine from St Pats in the US for about US$50.

Mine has the scale 0-32 brix which is what I'd recommend, although I haven't gone above the mid-twenties. Leaves room for those big barley wines :D

Readings are done in degrees Brix which is the same as degrees Plato.
I made a conversion table that I printed and laminated that I use to convert to SG.
You can find it in an earlier post in this thread.

I've attached a picture of mine.

It can replace your hydrometer, however I only use it when brewing to measure the run-off when sparging, as measuring the SG of fermented wort requires additional calculations to convert to SG as the alcohol in the sample changes things.


I also tried to take a picture through the view-finder.
You can just make out the scale but not really the numbers (0-32).

When you put a drop of wort on the prism and look through the view finder you take a reading off the scale where the white section meets the blue section (not shown, it is all blue as I had no wort on the lens).


doc, do you take the reading from the strat of the blue, or where the blue becomes distinct,

I thought the refract. would have been more accurate!
When you have wort on the lens you get a distinct clear line where the blue meets white (in the pic I posted there was no wort on the lens, hence it is all blue).
You then read the number off the scale and covert to SG using the table I posted a while back.
Simple as.

yep, i got my refractomter, last saturday. My line is not sharp?
Turn the eye-piece to focus it like you would one lens on your binoculars.

i could be an idiot, (and have been one once or twice before), but this only sharpens the writing, not the 'blueness'.

Thanks for the help!
The only other thing to look for then is make sure that you have the lens cover down flat. If is not down flat (on top of the wort) then I've had mine hazy.

I ordered mine today and should have it in a week or so.Im in the process of downloading Doc's chart and cant wait to brew again when the unit gets here.Im getting the refractometer from the ebay guy too.

Doc..Is there any preboil gravities or beer styles that exceed SG 1.1435? If there is; is it possible to extend the chart to 40% brix?

i think your dreamin Linz... pre boil 1.1435 thats a very big beer!

What are you intending to make?

Just wondering if you're still using the same data that you posted back in Feb 2003. I've been playing around with the calculations for refractometers and there appears to be considerable difference in the results of Brix to SG conversion depending on the equation you use. The simple equation is just to multiply the Brix by 4, so 10Brix would be a SG of 1.040. Using your calculations it would be 1.041. Using an alternative formula reported in BYO magazine in November 2003, you would get a SG of 1.039. The formula that you used for the table is the same one used by the guy who makes PrimeTabs, which are a bit like Coopers Carbonation drops. The supposed Guru on the matter is a guy called Louis Bonham who came up with the formulas for ProMash.

The other significant difference is that ProMash uses a wort calibration factor set at the default value of 1.04. This is because Brix refractometers are meant to measure the percentage of sugar in a pure sucrose solution, but wort is not simply sugar and water, so you need to make a small correction for the non-sugar components. Using the PrimeTabs equation plus the calibration factor would equate to a Brix reading of 10 to 1.039 and using the the formula from the Nov 2003 BYO magazine would give a SG of 1.037.

So depending on the formula you use and if you calibrate for wort you could interpret a Brix reading of 10 as high as 1.041 or low as 1.037. I'm still not clear on what the best equation to use is. I suppose using ProMash takes away the need to try and work this out for yourself. If anyone has ProMash what does it measure 10 Brix as in SG?

Umm.. I have promash, just dont know how to use it.

For the refractometer wort gravity window, if you enter 10 Brix, and leave the correction factor as 1.04, it gives an sg of 1.03844 or 9.615 plato if that was the question.

Yep still using the same table I posted here a year ago.
I only use it (refractometer) on brew day when measuring run-off etc.

When the wort hits the fermenter I use the hydrometer to take my OG and then at the end of the brew for my FG. I base my alcohol calcs on these numbers.

I've never got around to using the other formulas that are out there for corrections to calc alcohol content with a refractometer. Hydrometer is simple enough to use it those situations.

I calculate my recipes on 70% eff but get over 80%. Therefore I usually end up finishing my sparge around 1.020. So even with the variation of the different formulas I think I'm still safe on not getting any astringent flavours.

It is an area if I had the time and equipment it would be good to do some research into. But I'd rather be brewing :D