A Sorolla sketch

I was scrolling through some Sorolla paintings on the net and I found this half finished painting by the Spanish master. I always look twice when I see an unfinished picture by a great artist. It often reveals their working methods. I am not an expert on Sorolla's technique and I have seen Sorolla's that were half finished and NOT done on a colored ground. But let me see what I can find in here.

• The painting is done on a colored ground, and that is what caught my attention. Because he is such a high key painter I find that a bit surprising. Usually high key painters work on a white ground. The ground looks like an earth red, either a red ocher, or maybe burnt sienna and it looks to me as if he has stained the canvas with it. I would suppose that was done with a rag and solvent, and then allowed to dry.
• I think that he sketched a few major lines with charcoal or a pencil. I see evidence of that around the table top and in the delineation of that unfinished chair on the left. But I don't think there is much drawing under here, just some cursory gesture lines and a few straight edge lines where he knew he would need them. As soon as he knew how he was going to fit the image onto the canvas he got out a brush.
• Next I think he began working with his black and starting with the female figure on the right began to define the figures and get the structure of the darks in the grouping of figures.
• After a very short time he grabbed a second brush loaded with flake white and starting next to the dark, left most figure began developing the lights, he loaded that passage with the white to get opacity and contrast there. I think he was working at enormous velocity. He had all or at least several of the figures before him. The guys in the hats could have been posed by a single model, but without a doubt the female figure at the right was standing before him as he worked. The grayer passages like the back wall are simply the flake white with a little black in it. He painted around the box holding the flowers on the left and the two chairs, leaving his ground visible. That let the ground do some of the drawing for him.
• Finally he painted in the plates and tchotchkes ( spell check doesn't like that word, suggested crotchless instead ) on the shelf in the background. There are a few places here where he left the ground behind to help his image along and a few dark accents. Then he put the cobalt down into the shadowed part of the tablecloth. He also hit that ladies sash in the middle of the picture with that.
  
• Notice how he picked out the figure of the woman on the right by using the transparency of the flake white allowing the ground to show through, so that his shadow note is warm and the opaque white represents the lights, and is cooler than the shadow note. Transparency gives him temperature control and value.....in white, no less. It is ordinary to do this sort of thing in black or umber over a brown ground, but doing it in white is tricky. That's a a nicer move, fast and easy.
• He then threw a little green, maybe chromium oxide or viridian for a few accents. one, two. three spots right across the middle of the canvas. Even money says he faked the one on the right for balance.
• The red notes in the standing figures across the middle ground are probably vermilion. That was in common use and appears to be about the right hue in the reproduction. Then for some reason he quit. I wonder why? Seems like he was off to a good start.
• This whole thing happened really fast. He pretty much painted it in black and white over a brown ground and the poked a few accent colors into it. ZAP!