Pre boil gravity

[SouthRidgeBC]

I just took two pre boil gravity readings, both at 69 degrees. One right after vorlauf and one at the end of sparge. The first was 82 and the second was 33. Beersmith says my boil gravity should be 71 and my est. OG should be 81. Am I screwed or am I taking my readings at wrong times? Any advice would be great! Thanks!

 

[stpug]

You should be pulling your preboil gravity reading from your boil kettle once you've reached your preboil volume, and have stirred your wort.

 

[SouthRidgeBC]

I knew it! Is there anyway I can estimate given the readings I have?

 

[stpug]

I knew it! Is there anyway I can estimate given the readings I have?

You could work backwards. Knowing the water:grist ratio and your vorlauf gravity, you could compare to kai's first runnings to determine an efficiency. The second reading indicates you still had decent sugars in your final runnings.

Overall, I wouldn't worry too much about the preboil gravity THIS TIME. I would concentrate on getting an accurate final gravity reading and final gravity volume. Once you determine this, you can use it to estimate your preboil gravity as long as you know the accurate preboil volume you started with.

I'll see if I can find kai's chart of first running gravities based on grist ratio.

 

[stpug]

Here it is:

Table 1 - Extract content or gravity of the first wort based on the mash thickness. 100% mash efficiency, 80% fine grind extract and 4% moisture content of the malt were assumed for the grist

In other words, if you know your qt/lb then you can look to see what a theoretical 100% efficiency reading should look like. Then use your first/vorlauf reading to determine how much below that value you are, and that should give you an estimated conversion/mash efficiency (assuming you did a good job rinsing the grains of their sugars).

Let's say you used a 1.25 qt/lb water:grist ratio and your vorlauf reading was 1.082.
Tables says you should be about 1.096 for 100% mash efficiency
(82/96)*100=85% mash efficiency

 

[SouthRidgeBC]

This is great! Thank you so much for your help, very informative and easily understanded, I love this forum. You would be correct with the 1.25 qt/lb, 85%, not bad, that's usually where I am. Thanks again!