This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
I have a few words to say about a cheap and effectual covering for green-houses, pits, etc., which will answer for the American climate, as it has answered for our severe winters in the northern parts of Germany for the last 30 years, to the greatest satisfaction, under all circumstances. According to the size of your lights, have a frame-work made, so if put on, to cover the whole light sufficient. Take paste-board of the most common kind - tar it well over, so that the tar will soak well in the paste-board - do it a second time - then, according to the size of the paste-board, nail it on to the above mentioned frame, and put so many lath in your frame-work as to make the paste-board tight, or rather keep it, when snow or rain is falling, from bending on the glass. After that is done, give the whole another tarring over with a better sort of tar. I forgot to mention that it is best to put the tar on when it is either boiled, or made thin by means of hot stones put into it. After that is done, take a fine sieve and sift some sand over the whole, which will give it a nice appearance, and prevent any sticking which might be left by the last tarring. This, done every second or third year, will keep these shutters for many years.
Any accidental hole can be repaired by sewing a piece of prepared paste-board in it. It is possible that many may think boards for shutters, cheaper and better than this; but any one acquainted with them, will know that the glass is very liable to be broken by them, besides getting so often out of repair, and being so very heavy when snow or rain falls on them. The way to secure these sashes, (or shutters,) must be left to any one's own choice.
P. S. It is the air, or space between the shutters and glass, which keeps the frost out.