I'm not sure, because I am German, but I think "coating" is the wrong word.
If you have a polyester fabric, they glue PU on it to waterproof it. During the process it's liquid, in the end it is a film, a kind of foil that is glued on it. Everybody knows it from a cheap rain jacket.
But with cotton fabric impregnation it works different!
It is more like with your nice new white sofa, if you invite a few people and offer them red wine...
In the morning you discover that there is a lovely red spot on it.
And impregnation of cotton tents works more or less like that!
The impregnation is liquid in the beginning, but the cotton fabric sucks it up and - different to your sofa - it is invisible.
That's why I recommend to use it how it is, because I think, the impregnation is still in it.
Because you have an outstanding connection to Tencate, please ask them
1. Which product, ready to use they recommend, but
2. How is the old traditional mixture which we found in the boy scout books hundred years ago.
There they wrote " in the pharmacie or drugstore you buy x, y and z, and mix it with xx parts of water...."
It would be very interesting, which mixture they recommend.
Probably it's the same like in the bottles, but costs only a quarter of the price.
Very interesting, if one owns large cotton tents!
And perhaps you also can get out where to buy it, if we need a bit more than for a single sheed like you.
