Transported with this prospect he sent for his wife, ordering her to dismiss his workmen, and convert his effects into money. Within half a year the bubble burst; the Revolution happened, De Keyser's friends could no longer be his protectors, his business decreased, and the pursuit of the philosopher's stone, to which he had recourse in his despair, completed his ruin. He died at the age of forty-five, about the year 1692. He left a daughter, whom he had taken great pains to instruct, and with success. She painted small portraits in oil, and copied well.