Waxed paper negatives are of two kinds.
The first used by Fox Talbot the image was made on paper sensitized with a silver nitrate solution. The developed negative was then waxed with what was similar to present day parafin. The wax was melted, coated on the negative and then blotted off with successive layers of blotters.
The second devised by Le Gray waxed the paper just after sensitizing it and then made the exposure.
When done correctly the wax is smooth, thin and hardly noticeable until one looks at the negative with transmitted light.
Waxing the paper negative makes it almost as transparent as film. I just completed a salt print from one owned by MoPA apparently from the 1840's, which was a real pleasure to print.