higher Preboil gravity

[brewmaster 2011]

I am having a problem with my gravities. my preboil gravities are about half a degree higher then my knock out gravities. anyone have a idea why?

[Diggity Dave]

How do you prevent boil overs? Are you using anti-foaming agents? If you are instead spraying down your kettle foam constantly, that could be the reason why you could have a higher preboil gravity

[brewmaster 2011]

i never have a boil over problem so i never have to spray it down

[ParishBrewingCo]

You either have a measurement problem (cooling to the correct hydrometer calibration temp? cracked hydrometer?) or you are adding water to the wort.

One source of water being added to the wort is in your HX. Could be leaking from cold side to wort through a bad gasket.

Where are you measuring knock-out gravity? From the kettle or after the HX?

[BrewerRev]

How are you measuring your gravity - hydrometer/saccharometer or refractometer? Are you taking temperature differences between your wort and the devices calibration point into account?

[brewmaster 2011]

my hx isn't leaking. and my saccrometers have a built in thermometer for temperature adjustments.

[Diggity Dave]

Are you steam or direct fire on your kettle? Maybe a leak on your wort side kettle?

[ParishBrewingCo]

WHERE are you sampling for your knock-out gravity?

[scott isham]

I have had similar problems and believe it is, at least in my case, wort stratification in the kettle. I gently stirred the wort with my mash paddle a few times and that seemed to be the answer.

[brewmaster 2011]

the steam jacket is not leaking into the kettle i take my preboil 5 minutes into the boil and i take my knock out at the fermenter

[gabewilson50]

I've found that highly aerated wort taken from the fermenter can sometimes give a lower than actual hydrometer reading. The air bubbles traveling up around the hydrometer can create a lower density immediately around the hydrometer. You may want to pull a sample from the kettle at the end of the boil and compare it to a sample from the fermenter.

[liammckenna]

Stratification in the kettle?

Let the kettle come to a full rolling boil before pulling your first sample.

Ensure your sample from the fermentor does not need de-carbonating prior to measure.

Luck.

Pax.

Liam

[a10t2]

How are you pulling the kettle sample? If it isn't covered while cooling you could be seeing an increase in gravity due to evaporation.

[dick murton]

I have expereince of a couple of breweries where the heater elents / burners are part way up the kettle walls and know that the bottom never gets thoroughly mixed in until later in the boil, if ever. Manual mixing or recirc from the hot middle region to the bottom, at least until fully up to boiling point might be the only answer

[gallon]

I have experienced the same issue. I've drawn a sample from the surface the whirlpool port and the bottom of the kettle and had all different readings. I think mixing is the answer as well but it still isn't always the same for me. Where do most people draw the pre-boil sample from? Also, I was wondering what most people go for a difference. I boil off about 1 degree Plato.

Thanks,
Tim