A slightly longer block to add careful shading, texture, or layered detail to a focused subject.



The extra five minutes over the sweet spot aren't for a bigger subject — they're for value and surface. Twenty minutes is where a drawing stops being a good outline and starts to look like it has weight and material.
Almost entirely into rendering. Build tone in layers — soft passes first, then deepening the shadows — so you're modelling form rather than filling in outlines. This is also enough time to characterise a real surface: the difference between the way you mark metal, fur, or glass starts to show up here.
Establish your construction fast — aim to finish the block-in inside the first third — so you protect a full twelve-plus minutes for shading. Then squint at the subject to collapse it into two or three value groups, and lay those in as whole regions before you chase any local detail.
The classic twenty-minute mistake is pushing your darks in too hard, too early, and ending up with a muddy grey where midtones and shadows blur together. Sneak up on the dark end gradually, and decide which spots stay pure paper-white before you start — reserved highlights are what make the rendered areas convincing.