Postboil Gravity vs Starting Gravity

[Jase]

Hi there,

I've been all grain for quite some time, but decided to try brewing my first Baltic Porter. My post-boil gravity was 1.082. I just put the beer onto ferment and got a starting gravity of 1.062. I double checked the starting gravity with both a hydrometer and a refractomter and both measured 1.062. All of my previous brews the post boil and starting gravities have been within a point or two of each . I did not add any additional water to the cube in case you have be wondering, so it wouldn't be volume difference that has caused the variance.

What may have caused the large variance in the gravity readings?

Cheers,
Jase

 

[meathead]

How did you measure the post boil gravity? If you used a hydrometer with hot wort it will be inaccurate

 

[Jase]

How did you measure the post boil gravity? If you used a hydrometer with hot wort it will be inaccurate

Hi Meathead,

I cooled a sample to 20 degrees and used my refractometer.

Cheers,
Jase

 

[Danscraftbeer]

It can only be a miss reading. Post boil and OG is the same thing unless your adding a large starter. Even then there shouldn't be that much difference. I've got misreadings with pre boil. Sometimes malt can current. I'm not sure what the word for it is but an accurate OG reading depends on good mixing just prior to taking the sample.
Eg: I've mixed the pitched wort very well but didn't take the reading until the next morning and it seemed I undershot on gravity a lot! eg: 1.046 when expected 1.052. It couldn't be right so I remixed/shake the brew then took a reading and it was spot on the estimate 1.052. All good as planned etc. I don't know what or how malt can seem to float or sink or something its a mystery to me...

 

[droid]

I think it's referred to as stratification where the liquid is not mixed and differing readings can occur.

At the end of the day your BG might have been affected by the above and even your FG if the wort was not mixed up properly, so it could be a bit of both.

If it was me I would think the BG was incorrect @1.082 and it was some kind of mis-reading which would then piss me off and I'd look at my efficiency. Do you use software? Do you brew big beers often?

 

[Dr_Rocks]

I think it's referred to as stratification where the liquid is not mixed and differing readings can occur.

At the end of the day your BG might have been affected by the above and even your FG if the wort was not mixed up properly, so it could be a bit of both.

If it was me I would think the BG was incorrect @1.082 and it was some kind of mis-reading which would then piss me off and I'd look at my efficiency. Do you use software? Do you brew big beers often?

I have been on the receiving end of stratification a couple of times now.

I've finally learnt to stir my wort/beer prior to sampling for gravity, however I don't think it will be the last time i succumb to this!

 

[droid]

I have been on the receiving end of stratification a couple of times now.

I've finally learnt to stir my wort/beer prior to sampling for gravity, however I don't think it will be the last time i succumb to this!

you'd know all about stratification eh Dr

 

[droid]

actually it wouldn't be a bit of both would it as the post boil liquid would be all the same G