I get cardboard boxes from from a variety of sources. When you have to be budget minded you can often get them from stores.
Sometimes I can get them from local stores from their own orders. One local pharmacy store throws them out back to be recycled. When I am in need I will watch for them to get them as fresh as possible. You can also just ask them when they get typically get orders delivered.
These often are blank, no printing on them because the smaller ones are boxes that were inside of larger boxes. The larger boxes are the ones that are dirty from shipping but the interior ones are clean enough for my need. They have emptied them of dry products for their shelves. I don’t get boxes from grocery stores or any source that could be wet goods.
With these smaller ones I can modify them, cut them down to size, to fit the painting.
Sometimes there are cardboard sheets I can use as well. They were dividers or sheets between layers.
For home storage larger paintings I have gone to Electronics stores and grabbed TV boxes to keep them in. They are the right proportions generally and it keeps them dust free.
You can also buy cardboard online. Google cardboard boxes and cardboard sheets.
U-line is a good one for both boxes and sheets meant for shipping, They are blank, no printing.
It is not hard to make a box from a sheet to fit a painting. It doesn’t have to be perfect as long as it protects the painting, the frame and keeps anything from touching the painted surface.
Remember, you can wrap that box in plastic, a plastic bag (from the dry cleaners for larger ones?) to protect it from water, and wrap it in bubble wrap for shipping, putting all that in a box to be shipped.
One note on shipping:
ALWAYS write the “To:” and “From:” on the box that contains the painting, the interior box wrapped in plastic and bubble wrap.
Why? Sometimes shipping boxes get destroyed or addresses get obliterated and then can’t be sent or returned in the middle of being shipped. I know this because I have received show paintings for The National Watercolor Society from all over the world for their shows. I have seen boxes torn to pieces and taped back together by the shipping company. It was a miracle the addresses were still legible otherwise they go into some warehouse and maybe identified and claimed through a search by the sender.
I have also seen post from other artists on Instagram who have had art sent to a gallery for their show get LOST, and never found.
ALWAYS HAVE THE “TO:” and “FROM:” SOMEWHERE ON THE INTERIOR of the package!
It may not happen often but it is a simple thing to do and is your safety net. Any box obliterated the shipping company would find that info, re-box it and continue it to it’s destination.
One final thing. I frame some work myself but I also make quick cardboard ‘sandwiches’ whenever I take paintings to a framer. I don’t care if it is only a short distance to drive. I spent hours painting it and it is safer than just throwing it in the car.
It is a cardboard sheet about one inch larger than the painting all the way around.
A second sheet of the same size serves as a lid.
Cut strips of cardboard one inch wide, stack and glue them together until those strips are taller than the painting. Example, I paint on wood. It is about 3/16’ thick (just thinner than a 1/4 inch) Three layers of strips glue together makes it thicker than the painting.
I glue the first two in an “L” to the sheet. I place the painting against that. I gently snug the other two up to the painting, mark with a pencil, remove the painting and glue them.
when done the painting will fit snug. Just remember to leave a finger slot on one side to easily remove the painting. So, one side is made of two pieces with a gap in the middle of the strip.
These are only meant for transport, not shipping but I use them over and over since I paint in the same 5 or 6 sizes. Smaller ones I put rubber bands around them to hold them closed. Others you can use blue tape.
I have not put a certificate of authenticity but is something I am considering now. It’s all about available time.
I have put what I call ‘painting plates’ It is a description of the painting, its info, date medium etc and I will add my thoughts about making it, what it is about, something like that. I hand sign it.
I put that on the back of the painting on the paper in an open envelope. It is like a card they can remove and read. Collectors love that because it is personal to that painting and it serves as a certificate of authenticity. I will probably rethink it and make it a certificate of authenticity still with the rest of the info and thoughts.
I print it on a quality heavy stock paper and hand sign it.