Fred,
I shall have to make another pilgrimage to the 'tute.

The concentric hammer blow pattern on the bottom shows how the base was tuned and leveled by planishing. That action also would have deepened the bowl.

The bowl was not particularly deep.
the 6.5" dia fold formed bowl I made was 2.1" deep.
At 14.625" Karl's bowl is over twice that diameter and only 2.875" deep so most of the shape was from the folding.

My bowl had a single sided flute in each radial pattern, The Nikrasoff bowl has double sided flutes which eat up lots of material. That was partially offset by the stretching the texture blows added to that portion of the radial flutes.
I think we may have more of a folded flamenco dress (added gores) here than a raised piece. The radial "cross peen" tool marks show that stretching has occurred around the circumference,

Gene Olson
Sculptor
Elk River, MN

Gene,
I think the reason for the stretching marks around the cicumference is because the rim is bent downwards. Whenever you raise and put a downward rim you have to stretch the metal. To me the bowl looked raised and then the flutes were added.

warren
http://www.metalrecipes.com

Warren,

Charles and I have been discussing this.
It seems that his definition of fold forming has to do with folding and then unfolding and perhaps refolding to obtain pattern remnants from the unfolded bends as part or all of the pattern, as such this piece probably escapes his definition as the folds were made in the places they were wanted and then never reworked (other than making them crisper/sharper)

Raising is not the major operation in the formation of this shape however. Raising involves pushing the material into itself by making ruffles or tucks and then pounding them back into the sheet, or by working it over a stake so that raised area being struck is driven down and into itself and the surrounding supporting area. The process of raising involves a change in surface area and an increase in thickness, (and sometimes a relocation of that volume to an adjacent area)

My thesis is that the shape is developed by folding or bending, like making an angle bracket, or a box, or a fluted coffee filter.
The entire bowl is one complex set of tucks, one complex set of ruffles, that if you pounded down into a uniform "cone" would give you a raised bowl, but if you step on it and squash it flat, will unfold back to a flat plate with a fold formed pattern on it. (Charles definition of fold formed) instead of a bowl.
That is the reason I did the sample bowl with a similar pattern. I folded the material along the pattern lines to create the shape. That there is further work in Karls bowl, in the textured flutes and the domed up (probably faceted by planishing with a flat hammer over a round stake) areas near the outer edge is obvious, but the making of a flat sheet into a similar bowl can happen without raising. Even turning the outer edge out and down can be done by adjusting the widths in the fold pattern.

There are several ways to go about it.
Marilyn suggested a good one for radial symmetry like this and then there is the way I did it.

I started the folds by tracing them with a hammer and stake moving along the bend line making the bend. kind of like if you took a spoon and clamped it in a vice, laid a piece of foil on it, and then pressed down with a finger just to the side of the tip. It would start a fold at that spot.
If you move the piece over the contact point following a line, you will start a bend in that pattern. It is point deformation.

Marilyn suggested bending a piece of steel strap to match the radial curve and sharpening the edges, then pounding the metal down over the edge of the strap with a soft hammer; after which you would move to the next location and repeat til done. Additional folding work would be required but you would get your geometry and a start all in one go.

G.

Gene Olson, Sculptor
Elk River, MN