A canvas that has not been stretched ships rolled inside a rigid tube; a stretched canvas ships flat inside a double box. The wrong decision here is what damages the paint on the way; the packing that follows either path is cheap and quick.
Same painting, different packages. Choose before you pack.
Roll the canvas with the paint facing out, not in. The paint layer sits on top of the fabric; rolling it inward compresses the paint and forces microcracks. Painted side out puts the paint on the outer curve, where it stretches instead of pinching.
Cut a piece of glassine (a smooth, chemically stable acid-free paper) an inch larger than the canvas on every side and lay it against the paint. Roll the canvas and glassine together onto a six-inch or larger inner diameter core, keeping the roll loose enough that the paint sees a large radius of curvature. Wrap the outside in kraft paper, tape the wrap, and slide the whole roll into a heavy triple-wall or PVC tube with an inch of room and end caps pushed home.
Cap both ends with the manufacturer's plugs, tape the caps with clear 3-inch tape, and add a label reading “Painting: do not bend or crush”. The tube is more likely to be dropped on an end than a side, so a snug fit matters more than exotic padding.
Once a canvas is on a wooden stretcher, the frame is what gets damaged in transit. The paint stays put; the corners split and the stretcher racks. The packing method is therefore about protecting the four corners and preventing the frame from twisting.
Cut glassine to just larger than the canvas face. Tape it to the sides of the stretcher, not to the paint. Add a layer of bubble wrap, small-cell side against the glassine, secured with painter's tape to the sides of the stretcher.
Cut a piece of double-wall cardboard the size of the face and lay it over the bubble. Tape the mask to the sides of the stretcher; this is what stops a corner impact from folding through to the paint.
Foam corner protectors (the ones frame shops sell in bulk) push over all four corners of the stretcher. This is where handling damage lands most often; the protectors distribute the load.
Inner box within a half inch of the stretcher on every side, outer box two inches larger on every side. Crumpled kraft paper in the void, packed tight enough that a hard shake moves nothing.
Do not roll: paintings older than a year (the paint film has cured and lost flexibility), paintings with heavy impasto (thick paint fractures under any curvature), oil sketches on wood or board, and any painting on hardboard, panel or masonite. All of those ship flat, corner-protected, double-boxed, on the same method a stretched canvas takes.
Do not ship a stretched painting rolled: the stretcher bars have to come off first, which is a job that changes the tension on the canvas and often damages the painting. A studio artist who intends to sell paintings rolled will ship the finished canvas rolled and let the buyer commission stretching at the other end.
A rolled canvas fits inside a Ground Advantage or Priority Mail long tube. Under about two pounds the two classes compete closely; over that, Ground Advantage almost always wins on all but the fastest lanes. A stretched canvas in a double box moves as a regular parcel; anything over the dimensions of a USPS parcel (108 inch length + girth) has to move UPS or FedEx.
USPS Priority and Ground Advantage include $100 of protection. Any painting sold for more than that should carry declared value to the sale price. On the site’s calculator the additional coverage is priced next to the base rate; buy it during checkout rather than after a claim.
Roll an unstretched canvas — the paint layer is more flexible than the stretcher frame. Ship a stretched canvas flat; the frame is what makes it fragile, and unstretching a painting for shipment is a job for a restorer, not a seller.
Only oil and acrylic paintings under about six months old, painted on a canvas without heavy impasto. Cracked or aged paint layers fracture when rolled; heavy impasto flakes. When in doubt, ship flat.
Six-inch inner diameter minimum for anything the size of a 24 by 36 canvas; eight-inch for larger. A tight roll cracks paint; a loose roll inside a small tube shifts and creases. The tube walls should be heavy triple-wall cardboard or PVC drainage pipe.
A layer of glassine cut to size against the paint, then bubble wrap, then a cardboard mask that shields the entire face. Foam corner protectors on all four corners. Everything then goes inside an inner box, which goes inside an outer box with two inches of cushion between.
For anything sold or worth over about $200, yes. The included $100 protection on USPS Priority Mail and Ground Advantage does not cover repair costs on a real painting; a torn canvas is a professional conservation bill. Buy declared value to the sale price at checkout.