Help me figure out my actual OG and FG please

[disney7]

I've screwed up, but not too bad I don't think. I bought my first hydrometer and turns out it is an all grain, marked for 155F. I didn't know there was a difference and I don't do all grain yet.

My OG was 1.120 at 68F (target was 1.100) and my FG was 1.060 at 46F (target was 1.029) as taken with the all grain hydrometer.

Any way to convert those numbers to what they would have been on a regular 68 degree hydrometer at the temps I listed?

 

[jester5120]

I've never heard of an all grain hydrometer. SG should be standard for any form of brewing. and are you saying it's calibrated for 155F rather than 60F (which is standard)

 

[CastleHollow]

The chart here

http://www.austinhomebrew.com/product_info.php?products_id=12972

only recalibrates down to 110F. Not sure if the relationship at lower temperatures is linear, but it appears that the adjustment is about -.001 to -.002 for every 5 degree variance from 155. Using that estimate, your OG would have been right at 1.097, so not far off your target. Don't think my math holds up all the way down to 46F, though.

Maybe you can take a reading of plain water at 46F, to obtain a zero-value and then do a rough calculation from there?

 

[disney7]

Thanks guys, I figured it out. The BeerAlchemy app from iTunes will calculate it. My OG was right on and my FG is fine too.

A hydrometer question though. When I drop it in the tube, it will read say, 1.040 and then within 20 seconds or so will drop to 1.030. Which reading is right? I've seen this phenomenon with every hydro I've tried, even the regular 68 degree calibrated versions.