My diamond is "real" oilcloth from a roll found in an old general store. It is not linseed based but I don't know what was used. I rolled it in newspaper and left it in the basement over the winter. It still oozed oil, so I ran it up an oak tree and let it weather. That was 0ver 20 years ago and the blamed thing will still transfer oil if you happen to put it on something absorbant.
There are different grades of drop cloths. Some are made of multiple lengths sewn together. These are guaranteed to leak at the seams. If you go to a paint store, you can find them with one or no seams and they are a bit heavier grade of material. A friend bought one, wadded it up into a 5 gal bucket and poured in a gallon of Thompson's Water Seal. He let it soak a couple of hours and then put it on the clothesline to dry.
We sewed a 6" x 6" elk hide in the center to prop the pole against. Instead of grommets, we used musket balls. Took several pieces of heavy twine and square knotted the ends together so we had loops. Then folded the loop back on itself to form a slipknot which was put over the musket ball and tightened. These never pull out like grommets and when the twine wears out, you just replace it.
I used mine in all types of weather and never got wet nor cold. However, in heavy rain or winter camp I rolled up inside of it instead of pitching it.
