Original gravity off a few points?.

[gusty]

G'day!, it's not a big issue but I'm trying to work out what, or if I'm doing something wrong.., the last few batches I've done I'm hitting all targets except my original gravity, I'm missing it by 3-4 points but I hit my pre boil gravity/ volumes and post boil volume but I'm down a couple of OG points??, I'm using beersmith as my software.

 

[contrarian]

Sounds like a measurement issue as if your volumes pre and post boil are correct then your gravity should match. All you are doing during the boil is concentrating the wort.

What are you measuring volume and gravity with?

 

[antiphile]

For a contrarian, he's awfully bloody agreeable. The first thing I'd be checking ('cos I had the same problem), is to measure your boil-off rate and if necessary, drop it down in the appropriate equipment profile. The defaults are too high for my gear.

 

[Diesel80]

Hydro is out. Wort probably too warm when measuring?

 

[gusty]

Sounds like a measurement issue as if your volumes pre and post boil are correct then your gravity should match. All you are doing during the boil is concentrating the wort.

What are you measuring volume and gravity with?

I'm using a " dip stick ", it's accurate to half a litre...

 

[gusty]

Antiphile, I've set that up in the beginning, I'm losing 5 litres an hour through my system, I might double check my measuring stick.., not sure why all of a sudden I'm missing OG points though as I'm using the same tools?.

 

[contrarian]

I'm using a " dip stick ", it's accurate to half a litre...

How about for gravity? Seems odd that it would change when you're using the same measuring equipment.

I use a refractometer for measuring hot wort and normally if I take 3-4 different samples I get slightly different readings.

 

[gusty]

How about for gravity? Seems odd that it would change when you're using the same measuring equipment.

I use a refractometer for measuring hot wort and normally if I take 3-4 different samples I get slightly different readings.

I use a refractometer, I might test it today and double check the dip stick as well.

 

[gusty]

Well I just tested the refractometer and it was out 3 points!... Probably should of done that first, thanks for the help guys!.

 

[mofox1]

There is also this little chestnut: http://byo.com/hops/item/1313-refractometers

The SG reading is (most likely) calibrated for a pure sucrose solution. Wort is mainly maltose (around 50%), with other compositions of sucrose, glucose, maltotriose and others. This composition will change depending on your grain bill and mash regime.

If you are repeatedly using the same grain bill, and same mash regime, you can take a cooled hydrometer sample to determine a correction factor for the SG reading to obtain the "true" SG. This isn't to say you shouldn't use a refractometer when brewing, just be aware of its limitations.

 

[contrarian]

Well I just tested the refractometer and it was out 3 points!... Probably should of done that first, thanks for the help guys!.

Although does that adequately explain the difference between preboil and post boil gravities? Surely it would be 3 points out both times!

Next time take a few measurements as it really can vary a lot from sample to sample!