Anomaly-free thin layer of wax -- how?

[jlafferty]

Hi,

I've been experimenting with applying a very thin layer -- about the thickness of a single piece of Scotch brand tape -- of microcrystalline wax between two pieces of glass. I'm so far having no luck.

I've tried the following methods:

Spacing the glass apart by placing small strips of tape between them, and then wrapping the two with tape, I've submerged the entire setup in melted wax. Problem: air gets trapped in the space between the glass and is near impossible to remove (without resorting to a vacuum chamber, which I don't have).

Pouring a small bit of melted wax on one of the pieces of glass which has tape at its edges acting as spacers, then placing the other piece of glass ontop and applying even pressure. Problem: though both pieces of glass have been pre-heated and cleaned repeatedly, subtle anomalies and stratifications in the wax surface persist -- these are a mystery to me and I'm at a loss as to how to better apply the wax.

Do any of you have advice as to what techniques I should use? Essentially, I need to sandwich a very thin layer of wax between two round (49mm dia) pieces of glass to act as a focusing screen for an optical device, and so it must be free of bubbles and superficial anomalies.

Thanks,

- jim

[john500]

I don't know what you have access to, however, spin coating is another common way to get a thin film. Fix the bottom plate of glass to something spinning and then add the wax and allow it to "spread out". Attach the upper layer aftterwards.

Otherwise, you might want to increase the size of the vent slits in your tape spacers to make sure that you don't entrap the air (i.e. more room for the wax displaced air to escape).

[jlafferty]

Increasing the space diffuses too much light -- I'm now working with one layer of tape after having used up to four layers in the past and progressively getting thinner for better optical results.

The tradeoff, of course, is that the thinner the wax layer, the more difficult it is to apply a homogeneous surface.

Spinning seems pretty complex and I'm not sure it will produce what I need.

Thanks or your thoughts all the same.

- jim

[RobJim]

What if you dip one piece of glass into wax, make sure the wax totally covers the glass, then stick it onto another piece by touching edges together and then reducing the angle until they are parallel?

I've never done anything like this, but that's the only thing that came to mind. Well that and trying to use capillary action somehow.

[jlafferty]

Capillary action would be great, in fact, that's how the pros who make focus screens do it, but I don't know how to spurn it on.

I'm getting pretty good results now, simply from pouring wax over one piece of glass and then placing the other ontop -- I just need to keep everything super clean. Too often, contaminants get suspended in the wax, and it's a real effort to keep this from happening (i.e. all have failed so far.)

- jim