It appears that the fabric in the illumination is just a large flat piece of fabric, with different color trim at the bottom, secured at the top posts of the back and front of the seat by tying around a ball, which is likely part of the decoration on the wooden chair underneath. It doesn’t actually look like this chair has arms, and I believe the ball at the rear of the seat area is simply a poor choice on the part of the illuminator. Unfortunately, this image was pinned off Tumblr, I believe, and the attribution was lost long before I saw it. However, it appears to be 13th style, similar to (but not) the Morgan Bible. (Bonus points to anyone who can help ID the actual manuscript.)
The first problem is that simple flat pieces of fabric, while extremely easy to make or acquire, are much harder to keep in place. They blow in the wind, or get disarranged when people move around. Many people develop some type of sewn fabric cover to hide their modern camp chairs, and avoid the issues of loose fabric. I created a version of this covered chair for Dorcas, who has a lightweight chair of the pictured style. (The table will be folded down and not accessible.) Read my comments about hospitality, to understand why someone might choose this type of chair. Here, I’m going to talk about how to make a cover.
As I started draping fabric, I discovered a wonderful thing. As long as the chair in question has an open space in the back, between the seat and the backrest, and open space on the sides by the arms, a simple tube of fabric covers it beautifully. You simply put the tube of fabric around the chair, fold the excess fabric from the front over the seat and let it hang, fabric over the back and let it hang, and then tuck the fabric from over the arms down the sides and let them hang. So easy.
To know how much fabric you need, measure around the chair,from right front to left front, A-B-C-D. Also measure from the top of the arm, to the seat, across the seat to the other top of the arm. D-E-F-A. Add together. This example equaled 2 2/3 yards. (I would add extra on the next version, and go with a full 3 yards. The back of the chair leans back some, which I failed to account for. I probably used up more on the flat felled seam than I really intended as well.)
Cut fabric (linen in this case) to the specified length, and flat fell into a tube. (Yep, in a pinch, this could be an anglo-saxon peplos.) Measure up from the ground to the level of the seat (up to E) and attach ties to the inside of the tube at that distance from the ground at locations corresponding to the front and back seat corners. It WILL be a bit baggier across the front. This will help keep your chair cover in the right place, and not drag into the muck.
For Dorcas’ chair, I placed the flat felled seam at the right back. Cords are at 17″ from the bottom edge, as the ground is 18″. Spacing is 24″ across back, and 18″ toward front. Your chair might be differently sized. By tying the tube of fabric onto the chair, you not only prevent the bottom of the fabric from ending up in the mud, or under the leg, you also help keep everything together when carrying or packing. You do NOT have to take the cover off to pack it up. But you CAN take it off to wash if necessary.
Stitch a cord onto the top corners of the seat on the inside, and just a bit down from the top, on the outside. This would be visible if you use your chair in a modern setting without the cover, but it isn’t very noticeable.
Acquire some practice baseballs – I got a package of 6 for $5 – or wiffleballs – plastic globes with holes cut in them. (you could also use plastic practice golf balls for the same purpose, they would just be smaller and more understated.) Cut a small chunk of the balls out – then they will be able to fit over the corners of the top back. (The photo shows one on the chair, before I stitched the cords on.) Use the cords you sewed on to secure the balls. I used a total of 3 yards of cord between the ties sewn to the chair, and the ties sewn to the tube.
I did attempt to secure balls at the front of the arms, where your hands would rest, using rubber lined clamps, bolts, washers & wing nuts, and some cord to secure the ball to the clamp, so everything would stay put at the front of the armrest. What I discovered is that a 3/4 inch clamp was way too small, and the 1 inch clamp was too loose. I couldn’t get the balls at the front to stay put, as they moved when you sat down. I’m not sure that wasn’t partly because the linen pulled on it, but the clamps simply didn’t attach securely. I hesitated to screw the balls onto the arms – as this type of chair is as light as it can be manufactured. (9 pounds) Drilling a hole in the arms risked weakening it significantly. So that design feature got eliminated. (If anyone solves this engineering task with supplies you can get at any hardware store, more bonus points.)
Now the final step. Put your tube over the chair. Attach the ties to pipe near the seat edge to keep the bottom off the ground. Make sure the slack in in the front. (you need it so the fabric drapes over the seat properly). Tuck the fabric from the front over and behind the seat. Tuck the fabric from the back over and behind the seat. Tuck the fabric on the sides over the arms and down on the sides of the seat. Voila, the entire modern chair is covered.
To secure everything, use your decorative ties with tassels to tie around each of the four balls. (I picked them up super cheap – any cord would do, we don’t see it in the illumination.) The final touch is a separate pillow cushion. I picked some up at the thrift store for $5 each. The separate pillow is pretty important for the look. We see cushions (sometimes with tassels at the corners) being used on benches as well, so it was common in period. In this case, it makes the chair even more comfortable, a great bonus.
Your chair now resembles the illumination. Your chair cover doesn’t have to be taken off to fold. The total added weight is minimal, which is often very important.
Want to take it a step further? The original image appears to have some type of decorative trim – block printing would be an easy way to achieve that.