Once again I have seen someone state with absolute certainty that 'vadmal' (or vadmel) is made by weaving a very open cloth then fulling it significantly.
Based on my research into wet finishing and fulling, my extensive experiments into fulling a great variety of woolen cloths, same yarn, different densities, creating different qualities of cloth from lightly to heavily fulled I suspect that weaving it open was not done.
Traveling to Sweden and being privy to the research done by a Swedish weaver who found a masters thesis detailing (in the 1940s) how vadmal was made, based on the memories of people still living who had participated in the making of vadmal when it was still a home industry.
Going to Norway to use a vadmalstampp to full cloth I'd woven, then observed how the webs brought by the rest of the group responded to the hammer mill.
So - my experiences with weaving extremely open to very dense woolen yarn than fulling it have given me some insights. When I wove extremely open, the web was exceptionally unstable and distorted even in the loom. There simply wasn't enough stability for it to create anything but a hair pulling experience as the threads moved, shifted, gathered too closely together, then slid too far apart in various areas.
However, I had been told that in order to weave this quality of cloth you *had* to weave 'window screening'.
Then in the water, the cloth took forever to full and stabilize - which was not unexpected, but the final nail in that coffin (so to speak) was the extreme dimensional loss. Massive shrinkage.
For all the headache of trying to weave a consistent unstable cloth only to have most of it disappear in the wet finishing did not seem like something my ancestors would have suffered gladly. Unless there was good reason.
Then the masters thesis, interviewing elders who remembered how their elders made vadmal - it was anything but window screening - quite the opposite! The fulling was 'extreme' because such a dense cloth was going to resist fulling. However, in the end, dimensional loss wasn't huge, but within more acceptable ranges.
Based on this information, I offered to bring a significant length of cloth to full in the hammermill in Norway. We'd been told to bring 100 meters of cloth to make it worth our while to rent the mill for the weekend. So I suggested that the other five decide how much each of them would bring and I would bring the rest. When I left for Sweden, I had two large suitcases filled with 15 meters of cloth each, plus my carryon with my personal items.
Since there were two 'basins' and I had two pieces of cloth (and because I didn't speak Swedish and didn't realize what was going on) the rest voted and declared me the winner of the first spot. I think they figured if I was crazy enough to bring 30 meters of cloth, I'd be crazy enough to go first and work out how the mill worked. :D
I had access to a very nice fairly fine Swedish woolen singles - finer than commonly available in North America - and used that yarn. I'd woven with it previously, used the 2 ply version in Magic in the Water, in fact, and had experimented with fulling it at a more 'normal' density. For this experiment I increased the epi and wove it more densely, although not as high as I would have done if I was trying to make actual vadmal.
It was a compromise between the ancient and the modern. Besides, I'm Canadian, not Swedish or Norwegian, so I figured I could do whatever I wanted. :D
The cloth was fulled in the mill for 90 minutes. In the end it would not, to my mind, qualify as vadmal or even wool melton (probably the closest modern cloth equivalent) but it was a nice quality of fabric that could be cut and sewn without it falling apart, was stable and still had a nice drape to it.
Some of the others brought webs woven with thicker 2 ply yarns, one in particular had read the modern literature stating 'window screening' and woven hers in that manner.
As the hammer mill pushed and pummeled her cloth, the threads slipped and slid and the cloth became uneven. She'd made enough that she could cut around the gaps, but the others were non-plussed (I wasn't - I had a pretty good idea that would happen, but it was already woven, not much point my saying anything.)
One person used a worsted wool, which didn't much want to full but did after a long hard pummeling in the mill. The others did less extreme webs and got decent - although much thicker than they expected - cloth.
Because part of the fulling process means that the web will grow thicker as it shrinks warp and weft-wise.
I decided to check a couple of books in my library. One is Fabric Science - the textbook that used to be used for the textile school in Syracuse, NY. Since I know wool melton is the closest modern cloth we have to the quality of cloth made called vadmal, I checked the definition of melton. Fabric Science says:
Heavyweight, closely woven woolen fabric, completely fulled i.e. felted) with nap. Used for coats and uniforms.
I checked a much older book - Groziki's Watson's Textile Design and Colour. I have the 7th edition but the first one was published in 1912. It goes into more detail saying:
A woollen cloth which is heavily milled, so as to form a firm foundation, and the fibres are drawn on to the surface by raising, but in the cropping process, which follows, the fibres are reduced in length so as to form a short, dense, non-lustrous pile. Usually woven plain or broken 2-and-2 twill - about 160 to 95 tex warp and weft, 10 to 14 ends and picks per cm in the loom. Contraction abut 35 per cent in width and 25 per cent in length.
A rough conversion puts this yarn at around the same thickness as a fairly common cotton yarn - around 2/8 or so - with 10-14 epcm or less than 1/2". (If I've done the conversion incorrectly, let me know and I'll correct it.)
Not open. Not even close to open.
I have also had the fortunate happenstance of being able to examine very closely samples of 'standard' woolen cloth from the 1700s. I wasn't able to do a comprehensive examination, but I would say these fabrics are likely very similar to the cloth described as melton - or vadmal.
Further reading Else Ostergard's book Woven into the Earth and her extremely detailed study of the textile finds from the permafrost burials in Greenalnd from the 900s to the 1400s - the time when 'vadmal' would have been a very common quality of cloth. Details of the yarn - how it was spun, and speculation on how it was woven.
I find the specification of dimensional loss of the warp and weft for melton (in my experience it is frequently different warp and weft-wise) of 25 to 35% right in line with the experiments I have done.
So everything I have found suggests that vadmal was NOT woven 'window screening' open, but rather more densely and then heavily fulled using mechanical assistance. There are many records in England, for example, detailing how many hammermills there were in existence in medieval times and Ken Follett, in his book Pillars of the Earth, details how the hammer mills thumped continuously fulling the cloth being made in the area, then used as trade goods. England made much of it's money for centuries exporting their woolen cloth, and it would seem that Scandinavians did for many years as well.
As for weaving 'vadmal' now in the 21st century? I would suggest NOT weaving it 'window screening' open, but choose a more appropriate density based on the thickness of the yarn. Then weave some samples. Experiment with density, weave structure and duration of fulling.
Choose your expert. Then become knowledgeable enough to be your own expert...