starter OG varies?

[rebel_scum]

So I just made what I thought was going to be a 1.5L starter for my upcoming Pliny brew- I have always used a ratio of 5 cups of water to 1 cup DME and had pretty close to a 1.040 starter in the past.

I don't check the OG of the starter every time, but tonight I used 10 cups of water and 2 cups light DME, and right at the protein break I took a refractometer reading- and it was at 1.095!?!

So after boiling it down for 10 minutes, I added water until I got it down to 1.039, and I wound up having to use 16 cups of water total to get to the desired reading. I checked my refract with distilled water- it read 0- and I blew the sample on the glass a few times to get the temp down a bit.

My questions-

Why did it take so much water to get the desired gravity when I have used much less in the past?

Is there anything I can do with the excess starter wort now? I can do a double brew day as soon as the starter(s) are ready but I only have 1 flask and 1 stirplate. (I wont be around enough tomorrow to feasibly do the occasional shake method). Is there a way I can put the excess in the fridge and pitch the yeast when the first starter is done in a day or so?

Thanks in advance for any help!-

 

[HaDaL]

I think your calculations are somehow off as well as your measurements.The volume of 1 standard cup is about 237ml and the weight of 1 cup DME is about 173g (density of DME is about 1.367).So based of sg equation, 5 cups water(1.2lit) and 1 cup DME(173g) should give sg number about 1.054 and similarly 10 cups water plus 2 cups DME should give same sg number.What was the volume of wort after boil?Unless the volume of wort was halved after boiling to reach such a high sg number.You can simply calculate needed DME with following equation:

Weight of DME=(SG-1)×V×2.7​

For example You want 2 litres starter whit 1.036 sg so
Weight of DME=(1.036-1)×2×2.7=0.194 kg or 194 g
To calculate needed water You must consider the evaporation percentage as well as the volume of DME which increases the initial volume of water.(each 1kg DME add about 640 ml to the volume)
Added volume by DME =W×0.640=0.194×0.64=0.124 lit
Volume of water needed={final volume÷(1-evaporation%)}-(Added volume by DME)
If your system evaporation is about for example 5% after 15 min boil so You will need {2÷(1-0.05)}-0.124=1.98 litres water
1.98 lit÷0.237=8.35 cups Water
0.194 kg÷0.173=1.12 cups DME

Is there anything I can do with the excess starter wort now?

Yes You can freeze that wort in a sanitized container to use in future.

 

[rebel_scum]

Now that is likely the most complete and concise answer I have ever received on a question! Thanks for the great info! I will use that formula moving forward and hopefully avoid any more issues.

Thanks for the assist!



Sent from my iPad using Home Brew