• Make a bead lens: With instructor supervision you can heat a glass thread over a low flame. The molten glass balls up and forms a clear bead.
  • Bend a scrap of aluminum cut from a drink can and punch a tiny hole with an ice pick or awl, about half the diameter of the glass bead.
  • the bead in the hole and hold it all together with a bit of tape.
  • You now have the optical system for a powerful, hand-held microscope.
  • A needle can hold a drop of pond water, and with a bit of clay to hold the needle, you have a working Leeuwenhoek microscope.
  • Focus by moving the needle up to the bead lens. If you hold the microscope very close to your eye, you may be able to see some of the sights seen by Antony Van Leeuwenhoek some 300 years ago.

Van Leeuwenhoek's interest in microscopes and a familiarity with glass processing led to one of the most significant developments in the history of science. By placing the middle of a small rod of soda lime glass in a hot flame, Van Leeuwenhoek could pull the hot section apart like taffy to create two long whiskers of glass. By then reinserting the end of one whisker into the flame, he could create a very small, high-quality glass sphere. These spheres became the lenses of his microscopes, with the smallest spheres providing the highest magnifications. An experienced businessman, Leeuwenhoek realized that if his simple method for creating the critically important lens was revealed, the scientific community of his time would likely disregard or even forget his role in microscopy. He therefore allowed others to believe that he was laboriously spending most of his nights and free time grinding increasingly tiny lenses to use in his microscopes. Leeuwenhoek constructed hundreds of microscopes and nourished a passion for building new microscope whenever he chanced upon an interesting specimen that he wanted to preserve.
It will probably never be known whether van Leeuwenhoek really ground his lensesas he wanted all to believe. His constant dissembling that his construction method required prodigious time, skill and effort is consistent with his general reluctance to teach or encourage competitors. It has been conjectured (with no direct evidence) that he actually copied Hooke's recipe and made lenses by pulling and fusing spherical globules with smoother surfaces than he could ever have achieved by grinding. German traveling bloviator Zacharias Konrad Zetloch von Uffenbach, after a long visit during which van Leeuwenhoek courteously entertained him with a myriad of wonders, ungraciously wrote in his memoir:
  • When we further inquired of Herr Leeuwenhoek whether he ground all his lenses, and did not blow any? he denied this, but displayed great contempt for the blown glasses. He pointed out to us how thin his microscopia were, compared with others (This phrase seems to indicate that one man or the other had seen instruments of like construction that may have predated Antonj's own. - ed.), and how close together the laminae were between which the lens lay, so that no spherical glass could be thus mounted; all his lenses being ground, contrariwise, convex on both sides. As regards the blown glasses, Herr Leeuwenhoek assured us that he had succeeded, after ten years' speculation, in learning how to blow a serviceable kind of glasses which were not round. My brother was unwilling to believe this, but took it for a Dutch joke (a snide German euphemism for a lie - ed.); since it is impossible, by blowing, to form anything but a sphere, or rounded end. - von Uffenbach, 1710
Even so, it would seem an excessive investment of effort if each lens were laboriously ground rather than being made in a minute or two with a spirit lamp and a blowpipe. He often built a new microscope for each interesting specimen, unlike the modern method of using a single microscope and numerous mass-produced, disposable glass slides placed on a fixed or moveable stage. He treated the complete instruments as permanent settings for his choicest specimens, hence the hundreds he is believed to have constructed. Nobody ever recorded seeing him in the act of making a lens by any technique. In any case, single spherical or hand-ground biconvex lenses would have suffered from severe chromatic and spherical aberration.

Cell Phone Microscope

How magnification works.