BTW Martin, when I said “can’t duplicate it” I meant by using crystal malts (and other malts) to simulate that flavor. I did that prior to reading about reducing the gallon of wort. Now it’s just Golden Promise and an oz or two of roasted barley (ala Skotrat).
OK, so candymaking IS relevant. I made pralines a few years ago. The first time I boiled sugar up to 300F in a nice wide saute pan and the pralines were a beautiful creamy color. The next time I used a taller, narrow pot. Same end temperature, but it took 3-4 times as long to get there and the candy was a very dark, caramel color with heavy caramelized flavors. So the story is that the final temperature isn’t the goal, at least not alone. The amount of boiling it goes through getting to the end point affects the outcome.
I did this brew on Saturday. I may have not boiled it long enough. I was getting antsy as it was getting late. At around an hour and 40 minutes it darkened perceptively and the bubbles got bigger. I did reduce it to about a quart, but it did not look like LME, nor did I need a scraper as someone suggested above. It was the consistency of hot syrup I suppose.
In terms of recipe design I think I should have used less roasted barley also as I think I’ll be too dark for style. That really doesn’t matter to me much but it’s an easy fix for next time.
Did my Scottish 70/- this past weekend doing a single infusion mash with 1.5 qts of water/lb grain. For most of the concentrated boil the temp was 212 F and the boil looked “normal” for boiling wort. After reducing the wort by half, the temp began to rise slightly. After reducing the wort by about 2/3 the boil changed noticeably because the bubbles didn’t burst and the volume of the wort with bubbles suddenly doubled in size. The bubbles were brown, not white foam. The temps were fluctuating rapidly between 217-219 F because one moment my thermapen probe was in steam and the next it was in wort. I stopped the boil and added some wort from the main boil which made the whole thing easy to pour out. I got some nice toffee flavor from the concentrated wort. The concentrated boil added a lot of extra time to the brew day because I collected about 2 gallons of 1st runnings for a 10-gal batch. Next time I’ll put the concentrated boil on the biggest burner of the kitchen stove since burning doesn’t appear to be a factor until most of the water has evaporated. Maybe I’ll collect 1-gallon of 1st runnings and add a little DME as a shortcut next time.
I caramelized a portion of wort in my pressure cooker before. It makes the wort really dark and adds alot of caramel and toffee without reducing the liquid level. I did it in canning jars. I think I kept them at 15psi for about 2 hours.
Now that’s a neat idea. Generally you don’t get caramelization until the water is gone, but it is temperature dependent IIRC although the temp is pretty high for it, like 300 degrees. At 15 psi it’s only 250F so not really high enough. Sounds like the maillard rxns darkened the wort and resulted in some caramel aromas and flavors.
FWIW to get to 300F we’d need to be at 70 psi. Seems a little dangerous. 
Very interesting. What a great experiment for a club. Side by side comparisons on the 3 ways to caramelize wort! I wish my club were more interested in this type of thing.
Keep in mind caramelization is a bad term to use in conjunction with wort. You cannot get actually caramelization until the water is gone and the temp is much higher than boiling.
Correct, but this is actually valid in the context that it’s being used here. When you are doing a side boil of first runnings for a Scottish ale the point is to boil it down to caramel. I don’t use a candy thermometer, but I go until the wort looks and tastes like caramel. And it solidifies when you drizzle it on ice cream 
I took a few pictures when I was brewing my Wee Heavy yesterday since there have been a few threads on this subject recently. I’m not sure how they came out, but if there’s anything worth posting I’ll try to share them later.
Basically, the biggest sign that it’s ready (to me) is taste. It’s tough to know until you’ve done it, because the flavor of the concentrated wort is already a bit toffee-like up until you cross over into the caramel zone. But the flavor is strongly and distinctly caramel-like once you get to the right point, and noticeably different from the pre-caramelized wort.
I’ve only done this a couple of times, and I’ve never made candy. I don’t know if I trust my eyes more than my palate at this point, but I did notice one visual indicator that seems to coincide with the caramelization. The bubbles changed from rising evenly to rising in mounds. Instead of what seemed more or less like a sheet of regular-shaped bubbles rising out of the pot, one side of the pot tended to mound up a bit more than the other, and the bubbles in the center seemed smaller than the ones around it.
This is more or less what I’ve done, just by sight. When it boils down to the point that it is ~ the consistency of LME pretty much equates to tasting like caramel to me. Technically I could boil it further I suppose but that’s boiled down to ~ a quart, and if I have the caramel flavor and haven’t scorched it yet, I’m happy. Makes a really great Wee Heavy.