I've had a few people ask me about paste so here is what I know about it. I often use wheat or wheat starch paste when I'm making books. For a long time, I used wheat starch exclusively since I was able to get the starch at a local health food store for a very reasonable price; but, they don't carry it any more. Perhaps I was the only person buying it. I have seen it at the art supply store too, but for some reason the price triples when it becomes an art supply. I could extract the starch from the flour, but that's a messy process. So now I just use wheat flour. It is my understanding that paste made from wheat starch is a slightly weaker adhesive than paste made with flour; but, paste made with starch is more archival than paste made with flour.
So here is how I make paste. It's really easy. For a small batch of paste, you need:
2/3 cup cold water
2 tablespoons wheat starch or flour
For everyone who has switched to metric, that translates to:
160 ml water
30 ml flour
Some people recommend distilled water. Let the water saturate the starch for a few minutes and then whisk it until you have eliminated all the lumps.
Now put it into a pot and cook it. If you cook it on direct heat, it is important to be whisking or stirring constantly to prevent the paste from burning to the bottom of your pot.
To reduce the difficulties, I use a double-boiler to cook paste. When using a double-boiler, the paste is far less likely to burn (maybe impossible?) and it isn't necessary to stir constantly, just frequently.
Cook it for about 10 minutes. When it's hot it will be thick and runny like...glue! Let it cool completely. When it cools, it will be more gelatinous. So, since it becomes a gelatinous blob, just mix it and mash it up to make it smooth when you're ready to use it, so that you can spread it without lumps.
This kind of paste has a short shelf life - it will likely start to get watery and moldy within a week. It might live a bit longer if you keep it refrigerated and you can add a bit of water to your paste container - the water will just sit on top and create a seal to help delay the onset of mold. Just pour off the water when you're ready to use it.