i have been brewing with extract and grains- boil a partial volume and add the wort to water. i want to start hitting the target OG's so i want to get a bigger pot and do full boils. can i test the SG during the boil to see if i am there yet? and is there a calculation for my current method of partial boils added to water?

Yes their is but do yourself a favor & purchase a beer brewing program for your computer such as Promash or BeerSmith and they will do all the calculations for you. If you use the "Dilution Calculator" to check your OG 15 minutes before the end of your boil (partial or full boil) you can then adjust the OG by adding enough DME to bring the wort to the proper OG for the last15 minutes of the boil.

Happiness’s is a large brew kettle, many advantages to doing a full boil as opposed to a partial.

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The Czar

this may be stupid but- i can sample for SG during a full boil? how do you sample from your boiling pot? and then cool it to take a reading? plus- if my SG is a little low, do i boil longer or do i add some sort of sugar?

Sampling OG during a boil is fine but you will need to cool the wort to the calibration temp of your hydrometer (or close to it)

Using a metal ladle and ice or water bath should allow you to safely take a sample and cool it. Be sure to not contaminate your sample with water or ice. Be careful!

A refractometer can also be used and, because it uses only a few drops of wort, the sample can be cooled to calibration temps much quicker. I think the calibration temps on a refractometer also tend to be a little higher.

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TTFN