Needing Advise On Gum.

When you soak a stamp in water to remove of the paper does the process remove all gum from the back of the stamp. 2nd question, those stamps issued without gum during 1870 to 1889 were they postal used.If they were how were they used on covers since they had no gum to be sticked. Any inputs and feed backs most appreciated. Thanks.

Some gum is almost impossible to remove in water, for instance, some of Great Britain's Victorians, and Austrian stamps of the 1890s. Stamps originally issued without gum were stuck with glue of various kinds; some is water-soluble and leaves no trace, some will never come off (and stains) the stamp, reducing its value greatly.

There are several types of water-soluble gum used on stamps, namely arabic gum or acacia gum, starch, animal gelatin gum or glue, and modern synthetic gum. These are water soluble gums and they stay dry till you lick it and it becomes sticky. This is the property we use to adhere the stamp to an envelope or a postcard. Once it is soaked in water, it dissolves into the water. The stamps issued without gum were fixed on the envelopes by using starch paste, made by heating a water suspension of starch (flour). Starch is not soluble in cold water, but it is soluble in hot water. I remember when I lived in Japan when I was a child. There was always a jar of starch paste on the desk at the local post office, usually covered with flies. It was provided as food for the flies as well. We had to wave our hands to get rid of the flies before sticking our fingers to get the paste. Sometime we found insoluble lumps and they gave uneven and rough surface to the pasted stamps. But, who cares, we just wanted to mail the letters.

Thanks for the replies guys. Just another question,is there anyway to determine a used stamp whether it was issued with or without gum.Some old US stamps I have look so clean at the back without any traces of gum but yet they have postmarks and cancels. Thanks.