Experiments With Semi-Transparent Cover Paper

I bought this really beautiful semi-transparent handmade paper a while back and offered it as a cover possible for a custom wedding book. I have never worked with this paper before, nor any paper like it.

Note the color difference.
The small pieces are plain bookboard.
The larger has a white cardstock underlayer.

Bookboard is a medium to light brown color - a variation of cardboard color. So, semi-transparent papers allow that darker color to show through. In this instance I needed to find a way to make the space behind the cover paper white or near white so that it didn't interfere with the cover paper. I could think of two options, with two possibilities for Option 2.

1. Put some kind of white backing on the cover paper.
2. Cover the bookboard with something white.
1.  Gesso
2. White Paper

I have zero experience with adding backing to paper and wouldn't know where to begin. And it seems to me there would be a host of problems that could crop up, which I am not be prepared to deal with given my deadline. So, Option 1 is an easy "not this time."

One of my bookbinding colleagues
suggested using a foam brush to
evenly brush on thin coats.

As a painter, I always have a huge tub of white gesso hanging around. I had only one reservation about using gesso... bookboard is really just layers and layers of paper glued together, and even thick bookboard will warp when damp.  This is true even with when using routine glues like PVA. Gesso is pretty damp and would need several coats.

Likewise, I had two concerns about covering the bookboard with plain white paper.  What kind of paper wouldn't compromise the archival status of the book? And how would the additional layer of paper impact the adhesiveness? I don't want my cover papers bubbling or falling apart 6 months of even 6 years down the road.

Left: White paper, cream paper,
and bare board.
Right: two coats of gesso.

I decided to do some quick experimenting with scraps of my materials and see if there were any glaring problems.  Nothing jumped out at me.  Although more time consuming to do several coats of gesso per piece of bookboard, I felt better about the quality and process.

After one coat on the first side, I used a hairdryer on medium heat and low air settings to speed up the drying process, and within twenty seconds the first coat was dry.  I put the first coat on the opposite side and dried with the hairdryer. Repeating this process until I had four coats.  (Two coats would probably have been sufficient.)

Once each board was coated four times on each side, and dry to the touch, I layered them in wax paper and pressed them overnight to prevent warping.

The completed book.

The next day I was able to cover the bookboard with my semi-transparent paper and it looked beautiful!

Things to watch out for when using gesso on bookboard:

1. The adhesive will bind with the toothy gesso, and if you need to remove your paper, your gesso'd layer will peel off with the paper, leaving a visible spot of brown bookboard. If this happens, you can just dip your sponge brush in the gesso, cover the spot, dry with the hairdryer and you should be okay.
2. The thin coats of gesso will never fully cover the board.  There will be lighter and darker variations. I was worried these variations would show through with my semi-transparent handmade paper, but they didn't.