Greet's Middle Ages

Requoting diamond twill source

I mean to go look at this diamond twill...

 

Sounds like a re.seller who buys from these guys. I got mine direct at 
great prices, they do bulk as well if you
can be patient and wait if they do not have enough in stock. on them to 
put the order together.
Usually a couple of weeks for 10 or more. But well worth the wait and 
the blankets are great for cloaks. LOL.
Here is the direct link. Shhh it's a big secret kept by their 
re-sellers. LOL. http://www.loricamos.vizz.pl/tkanieuk.html

Sandy

On 2/08/2010 10:17 PM, LEWINS SHELAGH wrote:
> I got it from a friend who trades in Viking and Saxon wares, in England. I
> can put you in touch with him if you are interested.
>
> These are actually shawls / wide scarves. One would be enough for a top, or
> for an apron to hang down the front of an apron-dress. Or you might piece
> one into a more suitable shape for a small cloak - or make any number of
> hats, pouches, trimming strips etc. But you couldn't make a whole dress out
> of one. And because the colours vary (they are seconds, though I haven't
> seen any flaws in mine) I think you'd be hard-pressed to get enough the same
> to make a full garment. But I haven't seen his current stock, there might be
> 2 the same and that would probably do an apron-dress.

 Looks great to me! Pretty much looks like this down to the size of the repeats:

http://2.bp.blogspot.com/_35z6SrYO6Eo/TFWnCRpprXI/AAAAAAAAAGE/bzPGkvrkuPg/s1600/\
Broken+Diamond+twill.jpg
-which was based on the thread/pattern repeat counts at the higher end of the finer fabrics found from the period (gaps between repeats are still there because it was a sample piece and only lightly washed).

Brígiða Vadesbana
http://ooo-shiiiny.livejournal.com/
http://brigidavadesbana.blogspot.com/

 

RUM 2010

RUM was held less than an hour away this year, so I got to go.

The Royal University of Meridies is the annual big teaching event for the kingdom of Meridies, and it also hosts meetings for many of the kingdom's service groups, resulting in the usual problem of too many places to be at one time, and difficult decisions for someone like me, who has her hand in too many Yahoo! lists.

So I chose according to Most Pressing Responsibility, which was first that I'm the new chatelaine of Glynn Rhe, and there was a series of How To Be The Best Newcomer Supporter Ever classes offered by the chatelaine of the entire SCA, so of course I had to see what she was like.

(I've already broken one of her suggestions, in that it's been more than 72 hours and I hadn't blogged yet.  Oh well, I'm learning.)

But there were all sorts of other lovely ideas about expectations for demos, followup, what loaner gear should be like to encourage retention, etc.  I look forward to Baroness Marie's summary of what was talked about.

I also took Ailleaghan's "Medieval Foods for a Modern Palette" cooking class, in view of my Pressing Responsibility for feast this year, and feel a little better about having the skills to pull this off.  Neat tip about how to use Excel to keep track of amounts and repetition of ingredients - since I'm working hard to become an Excel monkey mundanely, this is fun.

I hauled around some cardweaving that I'm doing to bind the cut edges of Honnoria's diamond twill wrap Viking apron.  I think I've got a new loom design worked out, based on the archeological board finds that I've seen somewhere, probably in Collingwood's book.  (I don't have a new board yet, but I've been using a segment of my warping frame with only two pegs, and it's working fairly well, and would work better if it were wider and had a big hole in the tummy end.)  Sorry, no pics, still camera-less, and I haven't taken a moment to sketch yet.  Bad Greet.

I didn't make all the social rounds I usually do, having showed up Not Early that morning and skivving off in advance of approaching thunderstorms, but it was nice to catch up with those I saw.  Fun to see more developed Roman and Kentish kits coming along...I wanted to take pictures of Her Highness Lethrenn in her new Kentish, but...no camera.

I also wish I could have stayed for the singing, but mundane life called, and I missed the Viking, who stayed home to handle Stuff, and was asked about.  We plan next to visit Trimaris for 25th Year (I'm really looking forward to the Indian feast!) and think our next Meridian event will be MGT.

I can haz diamond twill!!

Remember this project?  From July?  Well, seeing the Wood and Woven merchant at Gulf Wars reminded me that I was OH-SO-CLOSE to having my own 5 yards of 20" wide diamond twill, without paying $30/yard for it.  It is cotton, but still...

Magical, watching the pattern appear.  If one didn't know about all the painstaking threading, it would seem easy.  Though, see those loose threads?  They're loose because I'd made a threading error, and at first the pattern showed up like this:

 Can you see the error?  Hint, it's dead center.  Look for where the diamonds don't line up.  Here's a help:

 

A bit left of center in this picture is an incomplete diamond, and, if you look closely, you can see two pairs of doubled threads.  If I'd continued weaving this, this error would have repeated all the way down the whole 5 yard length, creating a jog in the pattern.  Ick.  What to do?

Well, it's nice to be learning on slick cotton, and find the mistake soon.  You untie the warp threads, pull them out of the woven piece, re-thread them through the correct heddles, and weave them back, that's what you do.

 

Kind of scary, but I told myself "it's like frogging knitting", and pressed on.  The worst thing would have been that I'd somehow gotten off the entire repeat sequence, which meant that not only these six threads were wrong, but there was no way to put them in right and have the diamonds meet up again, but fortunately that didn't happen.  As I thought about it more, I realized it didn't happen because I took the extra step of dividing up my threads and heddles into repeats of twelve, per my pattern, so there was a consistent measure to return to.

I wove another foot after supper last night, and realized how to dance the treadles to keep up with where I am in the pattern, so I'm getting up some speed.  I'm not sure what to do with this fabric.  I could make a Viking apron with it, and actually match the Viking occasionally, but purple's not my favorite.  I could make a very nice present out of it.  I could perhaps sell it.  I have a lot of colored cotton, and want to play around with trim next - I figure I can crank out 4 pieces of 4" trim at the same time, in the same structure, but in different colorways.

Anybody have any orders?
 
 

 

Mailbag - About my Dorset loom

(not my pic, but the seller's)

My little Dorset loom gets the vast majority of email questions, and I'm going to start answering them here also, in the hopes that the surprising number of loom researchers and hopeful weavers can find what they're looking for more easily.

The latest asks particularly (I paraphrase, the reference is to the blog post where I got to try out an Oxaback loom):

 Did you ever go to Vavstuga for a weaving workshop?

I am getting interested in learning to weave, and still choosing a loom.  Many people want me to get a jack loom as opposed to a counterbalance.

Is it totally intimidating to learn to dress and weave on a Swedish loom? Or is it perfectly doable, with a good teacher? (This seems to be a common concern, trolling the weaving blogosphere.)

My response is as follows: Thanks for writing and all the kind words! I'm not sure I can be much help, honestly, as I'm barely ahead of you, really. My impression, gathered from the weaving group, and from places like WeaveZine/WeaveCast, is that a jack loom distorts the warp somewhat by pushing up the warp threads, whereas a countermarche pulls some threads down and some threads up, so it's the least stressing of the loom mechanisms. My experience, from weaving on that loom, is that it's incredibly smooth to use. My jack Dorset, 24" wide, four harnesses, four treadles, string heddles, is less so. I don't understand why people would send you to a jack...though it's widely recommended for other advantages that may have to do with size, its liveability as a piece of furniture, and warping ability. You are incredibly lucky to be so close to Vavstuga...I have not been, though it is on my life list. They will be able to answer your questions. My floor loom is similar to a Baby Wolf, made by Schacht. Schacht bought Dorset some years ago, and my loom was purchased from the weaver daughter of a deceased weaver. If you google Dorset loom, you'll probably find my entries on it, as people find me via that search often. It's what I need to have - I do so many non-weaving things, and I take stuff with me to public demos, that a smallish, folding, portable loom serves me well. If it had six harnesses instead of four, I could do more...but then again, four does an awful lot, and I'm sure I will give up weaving before I exhaust it. Now, as far as other looms, I would like a freestanding warp-weighted one....but that's especially for my historical re-creation of Migration Period Britain...and a two-beam tapestry one...for both Navajo rug weaving, and for Roman-era fine-gauge sheers. I know these things can be intimidating, and I think it helps to realize that there is a power in naivete...I boldly and foolishly go where many wiser minds fear to tread, and I end up with experience, and equipment, and projects. (Sometimes they follow me!) If it speaks to you, jump in! All you're going to lose is money and time, but you'll gain memories and wisdom, and that's all we get at the end of our days.

Good luck, and happy weaving!

~Greet

Edit: When hunting for pictures that were not mine, I found this nice comparison of jack vs. countermarche.

Trying it out on someone else's loom...

Since I took Thora Sharptooth's wadmal class at Pennsic (see that entry here), Grainne and I have been saying we ought to get together to work on her warp-weighted loom.

She had one, but it had been little more than a coat rack since its creation, and I was a great catalyst to get it going.  (I do this frequently - I show up and people get courage.  It's a wonderful thing.)

So this was yesterday afternoon.

In a bit less than three hours (and with much gabbing and giggling), we got a Pretty Durn Wide(tm) warp spaced out on her loom, chained into front and back warp.  She's just doing a tabby weave for starters, to figure out some of the basic loom mechanics.

Here's one of the surprises: Hire a Greet (or some other similarly tall, skinny, and flexible string maven) to feed you threads as you chain them from below.  Goes MUCH faster.

(the Greet in the machine....)

When I work on my own loom (when I get it), I'm going to have to train helpers to do the chaining, as I suspect my natural attributes mean I'll be the one inside the warp.

Grainne told me about the Yahoo! group about warp-weighted looms, and I'm very excited to find so many people who have struggled and overcome some challenges I saw ahead.  For example, I can now see several examples of how to have non-wall supported looms.  There's even great photo coverage of how to take a project in progress off the loom, roll it up in a special bag, and move all to another location.  Critical for my life of demos and events.  After the tent is done...loom is NEXT.

Wadmal class, Pennsic 2009

This will be an incomplete post, as I arrived on site too late for the first installment of Thora Sharptooth's class, but as the cloth in progress was very similar to the construction of my string skirt, I feel I can muddle through that on my own.  Thora's page on the warp-weighted loom; if you're interested in Viking stuff at all, look at her filing cabinet.

Wadmal is apparently 2/2 twill from Iceland.  It's woven on a warp-weighted loom.  We all got to do a bit of the process.

When I got there, the loom (and Thora) looked like this:

See the narrow sticks at the top? They have been woven through the warp threads in 2/2 twill, counted to be the right arrangement.  This twill went like this: stick 1 was woven through in pairs.  Then stick 2 started with a 1, continued in pairs, and finished with a 1.  Stick 3 started with a pair, but the alternate pair to stick 1.  And stick 4 I think was the "default" shed, so no heddles were necessary.

So, what's going on here, is "knitting the heddles."  Heddles are the thread loops that, attached to each of several heddle bars (those closet rods flapping around), control which threads are raised, creating one of four different shed space combinations.  Obviously, the heddles make the pattern, so getting them right and evenly proportioned for tension aspects is important.

We each tried out knitting a few heddles.

One passed the spool of linen (in his hand) behind the pair of warp threads shown by the pattern rods, over the heddle rod, reached under the heddle rod for the thread "neck", stretched the neck out, twisted it 180 degrees, and passed the spool of thread through.  The stitch is very close to knitting.

(here's the pattern rods, as well as the top of the loom)

(the lower part of the loom)  Those uprights are there to help control the heddle rods, which tend to wobble on you when they're loose.  Especially now, in the knitting of the heddles, it's important to keep them stable, so they're lashed to the loom structure with thongs.

When you have your heddles knitted correctly, you can lift the heddle bar, and the pattern stick should drop out easily.

(a good view of the warp weights - can you see how they're bound up by the distribution of warp threads?  I've pondered about this a good deal, how do you manage to not fight the loom weights?  You regroup them for your pattern when you're done setting the structure.)

That thinner stick is the default shed rod, and it's showing us how the warp threads need to be redistributed amongst the weights so it can clear its shed properly.

Untying.

Redistributing, still 6 threads per weight, but a different 6.  Multiples of 12 seem to be useful for this loom, and apparently loomweights are frequently found in groups of 3.

She's ready to start weaving, but I missed a picture.  See the two horizontal threads running underneath the cluster of heddle bars?  Those chain the threads in pairs, and are an ad hoc "reed", which manages spacing of the cloth threads.  One is worked on the front part of the default shed, and the other is worked on the back.

She's holding a sword beater, which is primarly used to open the sheds better, and only used once in four picks to actually beat (very gently) the weft into place.  There's a pin beater too, with which one scallops the weft into position.

Pulling hard on heddle rod, and clearing shed with sword beater.

The weft scalloped into place.

Juggling the heddle rods is quite a trick - the first one just floats on top of the work as you work with the second and the third.  The fourth is so stiff, that you push it backwards, through the loom - you see the shed opening here.

When all four rows have been woven, then you go back to the first heddle rod's shed, and beat carefully into place.  If you beat so hard that you lift the weights, you will end up with a weft-faced fabric.  Tabby has to be beaten every row, and hard.  But twill was very gentle.

Although the cloth we were weaving in the class was quite narrow, this loom can do 40" wide fabric - which is wider than I can weave comfortably on my 4-harness jack loom, and requires two people.  I've read speculation that looms could have easily been wider - this process is slow and deliberate, and I can now understand how it might be a two-person process.  Which would suggest to me that narrower fabrics found in extant garments would have been woven to a specific width, on purpose.

Second Yardage - Diamond 2/2 twill, 5th c - Warping, Part 1

Basic notes:

Warp Yarn: Medium Lilac, Mandarin Petit, 100% Egyptian cotton, produced in Norway.  50g skeins ~180m/skein.  Wash cold, air dry.  Iron 150dC max.  18 wraps/inch.  Z plied, S twist.  7-ply.  Color lot: 5226 5926.

Weft Yarn: Light Lilac, Wildflower DK, Plymouth, 51% cotton, 49% acrylic, made in Holland.  50g skeins ~137 yds/skein.  Other stats same.  Color lot 50 105.

Ends: 276, selvedges sleyed double.

Sett: 12 epi, in #6 reed.

Weave type: Diamond 2/2 twill, variation as shown in Dixon, page 85, top variant.

Historical reference: Fine worsted diamond twill of the Birka type from Vinjum, Sogn and Fjordane, Norway (fifth century), as shown in photograph on page 136 in;

Jorgensen, Lise Bender.  "Scandinavia, AD 400-1000."  The Cambridge History of Western Textiles, vol 1.  David Jenkins, editor.  Cambridge University Press.  2003.

(Note: obviously anything at only 18 wpi is not going to produce "fine" fabric, but I was given a lot of this yarn, so I worked with what I had.  I figure the larger size will make it easier to analyze the weave structure.)

Okay, here's the step by step with pictures, for Madhavi especially.

This is called a warping board.  What's happening here, is that I'm winding the yarn shown in skeins on the board in this pattern, which I've measured to be 5.5 yards - the limit of this particular board.  (I need a longer board; fortunately you can see that if I just make new horizontal pieces and insert my dowels in, I can reuse the side pieces.)  I have three skeins wrapped on the board, and will end up using eight skeins total for this warp.

The little yellow ties are to keep the warp from tangling as I move it to the loom.  A lot of the rather mystifying bits are merely tricks to keep the warp from tangling.  This not-fine yarn is not so much a problem - but imagine if I was using the very fine orange yarn in the previous post?  Actually, let's not.  :D

Here's my left hand, having just taken that lower left loop off the dowel, cut the loop (that's one end of my fabric, those cut ends) and knotted the warp to keep the ends together.

Still working with the warping board.  It's propped on the front beam of the loom.  Know how to chain parachute ropes?  Same idea.  Just trying to keep all the strands organized.

Okay, I've jumped ahead a couple of baby steps, since I didn't have a hand to hold the camera.  Here you see multiple warp chains made, and the chains are wrapped around the front beam of the loom.  The cross end (the top end of the warping board, where the yarn was wrapped in sort of a figure eight shape) has also been cut open, and all those ends (276) of them have been fished through that comb-thingy (called a reed, mounted in the beater).  Each slot in the reed currently holds two ends.  I'm going to change that at the edges, so that they're firmer, by moving a couple of threads in on each side, making the edge denser.

Let's go around the back side of the loom to see what it looks like.

Okay, so in the background of this picture you see the chains wrapped around the front beam.  The new purple warp is sleyed through the slots of the reed, and temporarily tied on the back side (cat protection).  What's all this other stuff in the heddles?

(more vocab:  The white vertical strings tied in the frames of the harnesses are called heddles.  These are just string, knotted to all be the same length, and to have a little hole in the middle.  That's where the warp threads go through, one per heddle.  Those are extra heddles piled up on the sides.  The frames go up and down when I press the foot pedals, which creates different places to throw the shuttle, and the combination of stringing the heddles different ways and pressing the pedals to select combinations of harnesses is what gives you crazy amounts of variation.  600 weaves in my four-harness loom manual.)

Okay, the other colored yarn is actually the leftover loom waste from my Doublewoven Shawl project.  It's not a bad idea to leave loom waste in place until you know what you're doing next...many weave structures are put through the heddles in a similar way, and if you know you ARE doing the same warp organization, one tip I've heard is to knot the old warp to the new warp, and drag it through.  It's not going to work for me here, though.  I'm changing structure...the Doubleweave was strung straight: 123412341234, and this structure will be on point: 1234321234321234321.  Well, actually, it's going to be: 412341432143.  I'll explain more about that in my next post, when I actually sit down and thread the heddles.

We'll also see the diagrams of what I'm trying to weave, and the photograph of my inspirational fragment.

No tiny gauge, please

Okay, so now I'm definitely in love with yardage, and started to wrap another warp with this stuff, thinking I'd try out a fine gauge:

Fail.

I didn't even empty one of those little spools.  I didn't like the way the thread cut into my fingers...I just felt like a slave to it, with no sensual return.  Gave it away, and cut the wrapped warp off my warping board.

Onto cushy colorful DK cotton, for playing in unbalanced twill structures!

First big weaving project done

Began with 5.5 yards of warp (that's the max length of my warping board), ended up with 4 yards, 30" total length, so that's 24" of loom waste.  The finished piece averages about 32" wide.

Yarns:  All of the dark brown weft is alpaca that I spun myself.  This is about two pounds-worth.  I learned that I don't really like spinning, and have just sold my spinning wheel, so I'll be forced to do the medieval thing and actually buy my yarn henceforth.

The blue warp is also alpaca, but commercial.  The orange warp is handspun, but sheep, and not by me...it was a present from someone who went to Ireland.  The taupe warp and weft is mystery wool that was a present, so was the rose warp.  The light gray weft at the top of this picture is more mystery wool, gifted by Mairi Ceilidh just at Midsummer Revel.  I have a lot more of that, and it was a pleasure to work with.

All of the warp yarns are pretty thick...DK weight at least, running to worsted weight.  I have them set at a bit more than 6 epi (the reed is 6, but I skipped a slot every inch).  These gaps were very apparent in the weaving, but not so much now that it's wet-finished.

The warp yarns are mostly thinner.  I started with an unplied version of the taupe, a sport weight, but my spinning and MC's yarn are definitely mostly fingering weight.  Mostly...did I say I didn't much like spinning?  All you people who ask me, "Greet, is there anything you can't do?"  Now we know.

AFTER WET FINISHING

Damp dimensions: 8" short of 5 yards, but still averaging 32".  Lost two inches to finishing.

I chose to "full" my piece in the bathtub.  I wanted as much control over it as I could get, but I also wanted to lock the fibers in warp and weft together, to protect the structure.

Here's what that looks like:

(yes, those are my feet)

Dirty, huh?  My books tell me that cloth not yet wet-finished is called "gray cloth", because it's dirty from the weaving process.  I don't think that my own weaving process made the cloth dirty...I think that all this grime is from the alpaca fleece I spun - all the dark brown yarn is naturally colored, from an animal called Midnight who lives outside Pensacola.

What I did:  I put a few inches of the hottest water my tub produces (probably right under 140 degrees, given that it has about 40' to travel from the hot water heater), and per instructions from Dixon, added a good lather of "mild detergent".  (I used cheap shampoo, because the alkali is pretty low and my ordinary laundering of wool responds well to shampoo.)  In went the dry fabric, I scrunched it up so that it wouldn't be folded, and stick together accidentally, and then walked on it.  I walked on it for about ten minutes, scrunching and unscrunching it to get all the bits abused evenly, and it was in the water for about twenty, while I fooled around with taking pictures and figuring out what to do next.  Rinsed with same temp (pure hot, administered with handheld showerhead), and squeezed it out gently with my feet.

Apparently there's a piece of equipment, a slatted roller, that you can use to roll your delicate, heavy, sopping wet wool textile on.  I don't have one of those, didn't even read ahead to find out about it.  But I had a couple of FedEx tubes and lots of towels.  Wrapped a couple of towels around the FedEx tube, and rolled the whole thing up and stashed it in the spare shower overnight.

This morning it was much drier (though the FedEx tube was mush...I have an idea on how to make an inexpensive slatted roller out of chicken wire, still to be used with towels) but still dampish on the inside end.  I laid it out flat, took the top picture, and re-rolled it with a fresh tube+towel.  Which looks like this:

That's actually the starting end of the weaving, which apparently has a header.  (Haven't really seen or thought about it in two years, so I am not sure what I had in mind, there.  Probably blindly following instructions.)  I'm going to leave it in, because this piece has so many beginner's lessons for demonstration.

Other (ahem) design features:

I didn't warp selvedges...have you ever noticed in yardage that the warp threads are generally much closer together, which gives the selvedge a different appearance?  Often the weave structure changes to tabby at the edge to be firmer.  These selvedges are like the rest of the fabric.

Minimal puckering at the centerfold!  Very proud of this, for the following reasons:

This textile was produced with a weaving technique called "doubleweave"...which is a tricksy way to produce cloth wider than the loom.  You need twice as many shafts as the cloth weave structure calls for...i.e. for tabby, you need two sheds, so on a jack loom, that's four shafts.  Doubleweave can be two layers of unconnected fabric, a tube, or open on one side and folded on the other.  That's what this is....so when I took it off the loom, I opened it up and had wide fabric.  Except for where I messed up.  Look at this:

This is immediately off the loom.  See where it's not unfolded?  That's where an error "sewed" the two layers together.  I did this error twice within a few inches at a demo.  I fixed them by cutting the warp thread at the open side, pulling those threads out, and then darning them back in with a needle at this point.  Because this cloth is made from large-gauge stuff, and the weave was simple tabby, it was easy to fix.

Close up of the errors.  See the lighter stripes, where threads are missing?  That's where I've pulled the wrong weft out already.  You can see how securely the wrong weft "sews" the fabric together.  Of course this function can be used for design, too...I've seen doubleweave projects where the weaver stuffed batting in a bunch of channels as the fabric was being produced...not sure how you wet-finish that sort of thing.

Maintaining straight edges while weaving is tough - there's a gadget called a "temple" that helps, though I haven't made/got one.  I was warned by the books to expect some tension strangeness at the fold if I couldn't keep that edge smooth...so minimal puckering means I'm doing a good job with the edges.  Good job = not pulling my weft too tight (more common) or too loose.

I tried while rerolling the piece this morning to yank it about a bit, and carefully lined up the edges to stack with themselves - if you're familar with blocking knitting, you understand this phenomenon.  You have the power with wet wool to affect its final shape in blocking - a bit of fine tuning on shape is possible, even desired, for geometric shapes like straight lines.

So.  It's finishing drying, and I think its character is pretty well set.  The drape is fantastic...a function of the loose weave.  I like the long fringe, even though I know it will get raggedy with use.  The color is too wild and contemporary in its changes to be clothing, and I'd be concerned about the unravel factor, so I think this will be a light blanket, to be folded diagonally and worn as a big cuddly shawl.  It's light, soft, and will be easy to pin through with my penannular brooch.

After it's dry, I'll machine zigzag twice in the middle of the length to secure the weave for cutting, and then cut between the zigzags.  I'll handsew the selvedges together, and then handturn down a hem.  Maybe this is a good time to learn that herringbone stitch...this project is sort of a Frankenproject, showing off all its construction aspects proudly.  I figure between this and my North Sea woolly dress, I should be set for warm things for Pennsic.

Dixon, Anne.  The Handweaver's Pattern Directory: Over 600 weaves for four-shaft looms.  Interweave Press, 2007.

Weaving my own yardage

Ann commented:

...you really need to weave your own fabric. If you do it with rectangles and triangle gores in the side, you'll need about 8 yards, but narrow--just a little over the width of your shoulders.

Yup, this is definitely on my list.  Thanks for the numbers!

I've been reading about 6thc North Sea cultures, and the shreds of weaves imprinted on the metal bling show diamond twills and linen repp...so that's my next loomweaving move, after I get the 5 yards of spin-to-doubleweave off the loom that's been there way too long.

A bit of a problem with needing 8 yards...I'm going to need to rig my warping board for the extra length - it only holds 5.5 yards.