Flashing and Burning (hopefully not crashing and burning)

[albada]

Split-grade burning works well! I used it on the sidewalk on the lower-right side of the left photo below (this is a photo of two 4x5 prints). I burned 00 (green), and got some texture that would have blocked white as you see in concrete elsewhere in the photo.

I like the result because there is minimal haloing around my burn. But burning all those little spots of concrete was impractical, so I tried flashing with paper with blue to its threshold, resulting in the right photo above. I also boosted grade from 2 to 3 because flashing reduces contrast.
My goal is to burn and dodge without resorting to heroics like making pin-aligned masks. Here are two rules I discovered:

1. Flashing is useful only when it's okay for light tones to have low contrast. That's because flashing results in an upswept curve.
2. If a straight print looks okay around grade 2, then when you add a separate flash, the main exposure should have its green-time cut in half. That will add one grade and yield nearly the correct exposure.

Does everyone already know these things? I've had an enlarger for around two years now, so I'm confident with normal printing, but these other techniques are still new to me.

Here's another comparison of a grade 2 straight print (left) and a grade 3 flash (right):

Motion blur ruined this shot, but it helped me learn about flashing. The flash on the right shows detail in the canopies over the cars, which blocked to paper-white on the left. Also, the trees in the top-background look soft and billowy with flash, and harsh without.

 

[awty]

Looks like you slightly fogged the paper. The trick with flashing is to gain highlight detail without fogging the paper.
You need to do a preflashing test strip to get any accuracy.

 

[Don_ih]

Preflashing "moves up" the minimal exposure needed for detail to appear in highlight sections of a print. This results in virtually no impact on the more dense parts of the print but might make some brighter midtones a bit darker. The resulting loss of contrast should only be due to detail appearing in what would otherwise be white.

You burn with a zero filter to get more detail in highlights without over-darkening the more dense areas of the print. You burn with a 5+ filter to accentuate or deepen the darker areas without muddying the highlights.

I find if I'm attempting any of those things, I'll ultimately not be happy with the print. Well, except for 5+ burning, which you can mostly either take or leave...

 

[grain elevator]

Looks like you slightly fogged the paper. The trick with flashing is to gain highlight detail without fogging the paper.
You need to do a preflashing test strip to get any accuracy.

Yes, and to be more specific, your tests need to include the actual printing exposure. A flashing exposure that by itself doesn't fog might still lead to a fogged print, together with the light that comes through even the densest bits of the negative+flare.

 

[ic-racer]

Good techniques to learn. Some tricks with color heads. One example: highlights don't respond much to blue light, so one can burn with white light instead of green. This can be a trick to use when it is easier to pull the "White" lever rather than cranking the Yellow knob to 150 and the Magenta knob to 0 for the burn.

 

[Ian Grant]

Increasing the contrast grade helps bring out and separate the shadow and lower mid-tone details, but this is at the expense of the highlights and this is where flashing helps retain them.

It's important to do a flashing test strip, this is a piece of paper partially covered, with a series of flash exposures, then developed for your normal dev time. I tend to use a multiple number of flashes, you are looking to see how many flashes are possible before fogging occurs in my case I flash in 0.4 second exposures, typically fogging is a round 5 flashes, I then would typically use 2 or 3 flashes. I'm able to do this with a second enlarger

As has been said the right-hand (bottom) print appears to be fogging via the flashing. It's the wrong approach for a negative/print like this, two bath development or split grade printing would work far better.

Ian