hydrometer accuracy

[Martin G]

Just a thought and not knowing the nature of the hydro error, but 4 points off 1018 is 1014, which depending on brew and mash temp doesn't sound stuck? You can get an idea of thermometer accuracy by taking temp of boiling water and tbe temp of crushed ice 60% in water (so ice touches bottom of cup).

[Belter]

Are you absolutely sure 1.018 isn't your FG?

[Aleman]

ok guys just spent the best part of an hour going through numerous posts on refractometers, now considering my original problem i read that they're not much good for reading FG. any thoughts?

I've heard that too, though I've never used one so can't say. Aleman will know.

Well I use my refractometer for checking fermentation progress . . . as in if the reading is still changing it's still fermenting

For FG (and OG come to that ) I use both my refractometer and my narrow range hydrometer. I use the difference between the tow OG readings to build up a database of correction factors so I can choose one for the refractometer that is appropriate to the beer style I'm brewing for use with the calculations for FG . . .The hydrometer reading of FG is used for the back calculation of OG just to complete the circle.

I've found the calculations for using the refractometer with fermenting wort to be good (accurate) at Sean Terrils page . . . Yes you have to use a correction factor (aka the Fudge Factor) and it differs between brews and styles, but you can soon get a feel for it once you have a few comparisons under your belt.

So yes I think a refractometer is a very useful tool, you just have to be aware of the instruments limitations.

[oldbloke]

Refractometers are good for OG but they're designed for sugar in water, once there's alcohol in there you have some fancy arithmetic to do, simpler to stick to the hydrometer.
My refractometer isn't an expensive one and agrees better with my back of envelope known sugars calls, whereas my hygrometers tend to optimism.

[johnluc]

Thank you Tony, very well explained, i can now see how it can be useful for all stages of fermentation, have just ordered a narrow range hydrometer and will order a refractometer. i will at least know my og & fg readings are correct just hope i can get over my stuck fermenttations, don't know what else to do, really getting me down now.
johnluc.

[Belter]

Where did you orde your hydrometer from? I can't find one on Alemans recommendation. Murphys is too expensive.

[MTW]

Where did you orde your hydrometer from? I can't find one on Alemans recommendation. Murphys is too expensive.

For <1.020, Hop and Grape. Offers a single point scale, so you can read 0.5 point as easy as 1 point on a typical hydrometer. As Aleman says, Hamstead Homebrew look like they do some in other ranges too, made by 'Alla'.

[johnluc]

Where did you orde your hydrometer from? I can't find one on Alemans recommendation. Murphys is too expensive.

ordered mine from Rob at The Malt Miller. hop & grape wanted £16+ delivery to France Rob was £3.20.

[Aleman]

Where did you orde your hydrometer from? I can't find one on Alemans recommendation. Murphys is too expensive.

Sorry This is my one from Hamstead home brew, I forget just how horrible that web site is to use

[MTW]

Where did you orde your hydrometer from? I can't find one on Alemans recommendation. Murphys is too expensive.

Sorry This is my one from Hamstead home brew, I forget just how horrible that web site is to use

Can't remember the last time I brewed a beer below 1.050 Might need to add 50% water with that one, or just buy the full range.

[MTW]

OK... My refractometer arrived today: the one that Jim has just bought. Seeing that Jim's got a refractometer thread going too, I could end up linking this.

I mixed up Aleman's 10g sugar in 90g water again, though this time the cheap hydrometer read 1.036, which tells me that the tolerances for making that solution are narrower than my Morrisons' digital scales (or something else) allow, seeing that last time I got 1.047!!!. The scales are accurate wthin 1g (EDIT: that's probably enough to be off] across the range, when I test with coins, so who knows... Anyway, having zeroed the refractometer with distilled water, both my cheap hydrometer and the refractometer read the same (1.037).

I then diluted it down somewhat, to bring it into the range of my finishing hydrometer. At that level, the reading on the cheap hydrometer varied hugely from the reading on which the refractometer and the finishing hydrometer agreed*:

* UPDATE: I did another test later on, starting at 1.052 and diluting 50/50 with water (taking readings at each step with all 3 instruments), so also 1.026, 1.013 and 1.006. In that test, they all matched within a degree or so all the way down, thought the finishing hyrometer is far easier to read. I can't explain the erroneous read with the cheap hydrometer below, though I did double check at the time. Weird. Anyway, all looks more consistent now.

1.011 on the refractometer:


1.011 on the finishing hydrometer:


1.018 (!) on the cheap hydrometer. This is rather bizarre, seeing that yesterday both hydrometers read within a degree of each other around 1.015, but there we go. I will continue to test.


All measurements taken at 20C and repeated.

I'm delighted with that refractometer - so easy to use on a brewday. I suspect I may end up getting a better hydrometer for the upper range, but having two tools that agree in the FG range is already a big plus.

[johnmac]

The other possibility is a narrow range hydrometer from say hamsted homebrew.

I bought one of those - it was way out of calibration. Took it back and found that all of what they had in stock was reading differently.