What's the deal with refractometers?

[Roaster]

I can't find any definitive info on the difference between hydrometers and refractometers measurements. The hydrometer is simple and reliable, but the refractometer I bought always gives me a different value. Except for water where both read 1.000. Is this a typical problem or is it the unit i bought? It has a scale for "SG Wort"
Some say the alcohol affects the reading, so it's only reliable at the start of the fermentation, others sound like they have no trouble.
A current batch of partially finished wort reads 1.023 by hydrometer and 1.035 by refractometer.
I'm starting a new run tomorrow and I'll compare starting density by both methods. I've never actually done that yet because I stopped using the refractometer as unreliable.

[mashani]

Refractometers are only useful with direct measurements for measuring your OG. To calculate FG requires math and the simple reality of it is your hydrometer is a better tool for doing it unless you enjoy headaches.

If you want to use the refractometer just to see if "it's done" without drawing off a large sample, you CAN do that. Just look for stable measurements, whatever they are. Just ignore what they are, they aren't your real FG. But if they remain stable for 3 days or so your batch is likely done.

[Beer-lord]

I've learned that refractometers are just another brewing tool and also learned that mine is .03 off from my hydrometer. I use mine as I mash and boil to get an idea where things are as well as during fermentation to once again, see where things are. As mashani says, for accurate measurements, stick to your hydrometer. The ones professionals use are a bit different but are much more accurate.

[RickBeer]

This and that ^^^

[mashani]

I've learned that refractometers are just another brewing tool and also learned that mine is .03 off from my hydrometer.

Depending on OG/ABV/attenuation it should actually fluctuate from that .03 value. That might work out for you though for batches that are all similarish in OG + attenuation.

[berryman]

Not long ago a refractometer was on my list of things to get for brewing. I have used them in the making of maple syrup and recycling antifreeze (not the same one LOL) but decided against it for the limited use. If want to go newest hi-tec. A tilt hydro is next, Yes might be off some on accuracy too, but would be better suited for brewing if want to spend money on gadgets.

[The_Professor]

For the first year I was brewing beer I did not measure SG.
I would check shot glass samples out of the Mr. Beer spigot. Really cloudy within the first few days, if not there is a problem. Then clearing and less sweet. Let it go 2 or more weeks depending on the stated gravity of the recipe.
Finally got a refractometer. OG usually comes out somewhere in the ballpark of what brewing software suggests. FG (using calculations) is a bit flakey but I am really just looking for fermentation to be done.
Usually in the end there is beer.

[Roaster]

Amen.
I broke another float tonight, by dropping it while in the protective sleeve thing. I'm starting to not care. I couldn't do my comparison test between the two types, again.
I'll just see what the results are when a start reading is taken with the refractometer, to compare one batch to the next.
I see posts by a lot of people who take the readings seriously though.