Boiling in extreme cold temperatures

[Coreyolf1]

Hey, so I live in Northern Canada, where average temperatures in February usually find themselves in the -30*C without windchill. It's extremely cold here and I have a few questions about boiling in this type of weather.

1 - I seem to be losing a lot of wort through the boil, I lose about 1 gallon per half hour. Should I aim at increasing pre-boil volume to hit a targeted 5.5 gallons post-boil?

2 - If I increase pre-boil volume, will that throw off my OG?

Thanks for all your help eh!

 

[IslandLizard]

-30°C? Yowsers!

If you boil off more than your mash calculator told you, you can just add plain (dechlorinized) water, because that's what's evaporating. If you can add boiling water, you can add as it boils off.

On most calculators you can dial in the boil off per hour in percent or volume. That should get you closer. As long as the kettle can hold the extra volume. And yes, your pre-boil gravity will be lower, but your OG should end up the same.

I always say it's easier to add some than to boiling it off, so being a bit conservative in the beginning is good. I hate to find a low OG and an extra gallon with 15' left, which is usually where I check, before adding the late hops.

 

[Coreyolf1]

Ok, I see. So when boiling, technically all that's evaporating is water? At the end of the boil, if I've boiled off more than I wanted to, then that just basically concentrates the wort more? So if my final boil volume comes to 4.5 gallons, I could just add 0.5 or 1 gallon of dechlorinized water and it should hit the expected OG?

Would regular spring water work for this?

 

[IslandLizard]

Technically, it's a bit more than water. It takes DMS and its precursors and other volatiles with it, such as hop and malt aromatics. What you smell during the boil is leaving the wort, permanently.

Topping up with .5 gallon (~10%) at the end is probably fine, but for larger amounts it would be better to add earlier before it gets that low, so your wort doesn't get too concentrated, darkening more than it should and creating more maillard reactions and caramelization. Unless you want them, then that's the way to do it, like old ales and barleywines are stewed for hours. The first runnings are boiled down first.

For most efficiency, sparging a bit more or longer is the better method. It adds a few ppg. As long as you're sure you'll be boiling it off.

Spring water would be fine.
You must go through a ton of propane under those conditions.

 

[edroberts]

I haven't seen that dramatic of a boil-off, but it certainly doesn't surprise me. You get the joys of both the extra dry air and super-adiabatic lapse rates to increase your boil-off. Rough estimate (if I did this correctly)... Temperature alone would give you 25% more boil-off potential than someone at 0C. That assuming that the influx of cold and dry air is maintained at the surface of the water. Again... just potential. My inner weather geek is happy.

If you have the ability, adding to pre-boil volume is probably best so it drives off DMS and other volatiles. OG wouldn't be impacted, but your pre-boil gravity would.

 

[Coreyolf1]

Thanks for the replies fellas, I'll do that.

P.S. as for propane usage...... yup.:fro: