Typically backdrops have a horizontal seam, because when hung the weight of the
drop and
bottom pipe will pull that seam tight. On a well-built
backdrop the seam is all but invisible.
Backdrops are typically made of heavy-weight
muslin. Canvass is unnecessary. You can get 120" wide
muslin readily at a theatric supply or
RoseBrand.com: Theatrical fabrics, stage curtains, backdrops, hardware and accessories. Maybe also at a fabric store. For much more money you can get wider widths and not have a seam at all. This is good for cycs but not usually necessary for painted drops.
Here are the steps I use in building a
backdrop:
-lay the two pieces of
muslin together face-to-face and stitch the horizontal seam. Use a heavy-weight polyester thread.
-lay out the
drop on the floor and
snap lines for the sides and bottom (or top)
-fold over the sides and top to the
snap line and
iron the
edge (makes hemming easier). cut/tear of excess if it's more than a couple inches
-double-fold the hems (so the cut
edge gets tucked inside the hem) and stitch the hems
-stitch jute
webbing (get it where you got your
muslin) along the back of the top. One stitch
line at the top and one at the bottom of the jute.
Grommet through the jute. (not through the stitch
line)
-Take a piece of excess fabric about 12" tall and the length of your
drop. Stitch it into a tube. Turn inside out so the seam ends up inside (run a string inside the tube as you stitch it to help turn it inside-out). Stitch this to the back of the
drop at the bottom, such that the bottom of the pocket will be an inch or so above the bottom of the
drop. This is your
pipe pocket. You want it to be hidden behind the
drop but just at the bottom.
-Lay the
drop back out on the floor
flat and square. Staple along the edges every couple inches. The
drop will shrink a lot, so staple it well.
-heat a pot of water and mix in laundry
starch (or corn
starch). Brush this into the
drop (many people use a broom to work it in). This will size (shrink) the
drop. You can also use watered-down paint, but
starch works better.
-paint away!
-to be flame-retardant, you should use an additive to the paint (
Rosco, from your theatrical supplier), then spray the back of the
drop with a proper retardant after painting (a different
Rosco product, or others). You can also use FR
muslin, but it has a tendency to leech out the salts as you paint.
Let me know if anything's unclear! Good luck!