IIRC there is a spray seal that you can apply to the chart to 'proof' it against a topping of varnish. I think it is a spray lacquer, but I would advise you to google that first. I have also used clear hair spray effectively, but try it on a similar piece of work first. Varnish will cause the ink to bleed so that is why you need to seal it first. Another way of sealing paper is to paint it with a thin mixture of lepages white glue and water. It will dry clear, although a bit cloudy. Do this on another document first to check if this is an effect you can tolerate. Once the glue is dry, or if you use laquer, then you can top it with varnish, although that is typically a soft finish that will scratch and peel eventually. Back in the 70 or early 80's there was a product that came in a can, and you would pour it over a plaque and it would self level, absolutely clear, and rock hard... but I can't remember the name of the product. I thought it was decoupage but that appears to be the process not the product. (Help me someone) Perhaps asking at an art or finer wood supply store may net you results. This would be an excellent finish for your chart table. I did google a similar product called Envirotex that may do the job. Good luck with your project... it is way cool!
