Regular Hydrometer v Portable Refractometer

[Chris_S]

i have two hydrometers and just recently bought a refractometer

I have 20L of beer that has been in the FV for 13 days and due for packaging

SG readings are at 1.010 & 1.011 on my hydrometers but the refractometer is displaying a reading of about 1.026

I believe I have correctly calibrated it, so why the vast difference in readings. Will boiled cooled water really throw off readings as opposed to using distilled water ?

 

[RichardM]

The refractomer is meant for taking readings before fermentation. IF there is alcohol present there you have to apply a correction factor, see Refractometer Calculator - Brewer's Friend

 

[Chris_S]

Ok, so the old hydrometers are still required for after fermentation SG’s

 

[RichardM]

Ok, so the old hydrometers are still required for after fermentation SG’s

You can use the refractomer as long as you make the corrections for alcohol being present.

 

[Horners]

Rarely use my refractometer these days. Hydrometer for SG and FG. Refracto I used to find useful for taking readings of hot wort to determine whether any liquoring back required but now just trust to the process that it will be there or there about.

 

[Chris_S]

You can use the refractomer as long as you make the corrections for alcohol being present.

Thanks for the information, will try it on the weekend

 

[peebee]

Refractometers are great tools for quick checks here and there (hot wort, fermentation progress, etc.). But having to make adjustments for alcohol content (which often means using an online calculator) is a bit of a pain. But the alcohol issue is just the well known one; refractometers generally use a "BRIX" scale which expects a sucrose solution. For beer a correction factor is applied (often about 1.04) to allow for it being a maltose/maltodextrin solution; again the online calculator does this and sometimes these calculators allow the factor to be "calibrated" (certainly offline computer calculators should be able to). The problem with the "factor" is that it changes as fermentation progresses (the proportion of simple sugars and longer chain sugars changes). But I've not noticed final gravities being more than 1 or 2 SG points out.

If you think the numbers are small and insignificant, think again: SG is a measurement with at least three decimal places! Some refractometers have "SG" scales; I hope this summary informs you just how useless those scales are.

Hydrometers? Well they're just fragile and break, cheap one's can have misaligned scales, they require huge samples to work in, and the scales can be difficult to read (I'm bias as the latter is a particular problem ... which glasses cannot fix before anyone pipes up).

The solution I use needs a calculator too, but an ordinary handheld one will do. There is no conversion to make it read as a hydrometer does, but then a hydrometer is only a tool for emulating the readings that this device delivers. It uses small samples (25ml, perhaps 10ml if your weighing scales are particularly good). It is a pyknometer. The reason they are not much used for brewing (the instrument is very cheap) is it requires good weighing scales but they have become cheaper recently, and those cheapo Chinese postage stamp ones that claim to weigh to 2 decimal places are not good! I've got some adequate scales for £30, but you can go mad and spend £130 on some!

I summarised pyknometers >here< (and the post following the linked one).