Head space in SS growler

[capt82]

I got a 128oz and a 169oz stainless steel double walled growler for xmas and am ready to use for first time. I plan to carbonate with priming sugar and use the 16g CO2 mini tap just for serving. How much head space is needed for optimal carb?

 

[VikeMan]

Optimal carbonation would require no headspace at all. But if you want to reduce oxygen pickup (and slow down staling), make the heasdspace very small, just big enough to allow a little expansion of the beer if it is subjected to higher temperatures.

That said, without seeing your growlers (which apparently accept a tap and CO2), you'll also want to make very sure that the CO2 input apparatus is not touching the beer.