Do you find that a mashout is necessary to ensure 100% conversion? I have been measuring mash gravity for the past 20 batches, but it has only been accurate for the last 7 or so since I started cooling samples in a sealed container. I have thus far found that every beer but one required raising the mash temperature at the end (sort of a mashout, but it varies from 158-170F depending on how much water is in the tun) to ensure complete conversion. After a 60 minute sacc rest I am several Plato low, I think 2-5 but I'd have to check my notes to be sure.
These results are confusing since I have heard a lot of people saying that a low adjunct mash is converted 'as soon as it hits the water'. There may be some starches that are not gelatinized at the mash temperatures I am using, but I'd like some independent confirmation of this from other brewer's observations.
Grist has been mostly Best Pils or Best Munich, with a 2-row and wheat base beer thrown in
Mill gap: .025" set by feeler gauges on the Barley Crusher
Grist is conditioned prior to milling with 1-2% water by mass
Mash temp has been 151-154 over the 7 beer span, losing 1-3° in the hour
Strike water volume is accurate to the nearest quart
Grist is measured on a scale accurate to the nearest 0.1 oz
Temperature is measured with the pro-accurate digital thermometer from NB, 32.0F in icy water and 213-214F at boiling (for wort).
Sample is gathered either into a 20 mL screw top test tube and immediately sealed, or in a 10 mL medical syringe.
The test tube is cooled by submerging in a water bath, and the syringe is cooled by running cold water over the outside. I tried submerging the syringe before but some water mixed with the sample and contaminated the reading. Both methods agree exactly when taken on the same mash.
Sample size is typically 1-5 mL read on an ATC refractometer after cooling until it does not feel warm to the touch.
Grist potential OG is calculated from typical malt analysis sheets for base malts and values found in Home Brewing Wiki's Malts chart for each malt used. Formula used: expected FW extract = 100 * grain laboratory extract / (R + grain laboratory extract) where R = water to grist ratio.