I was looking for the same answer. The website was hard to find and didn't have any suggestions, so I called Yasutomo directly to ask if the markers could be reconstituted. The answer was a flat "no." When I asked how long they should last, they said about 6 months. I have packages of all the colors that are now unusable. I bought them last year thinking they would last a while if I stored them tightly capped, inside plastic bags, inside a plastic storage box. Nope.