etching stencils revisited.... (again, and again)

[Ray Rogers]

BDH,

You're welcome. If you got a stencil to work with sunlight then that could be a strong indication that the problem is with your light bulb.

Cal,

The process we're discussing is a photo etching process to make a stencil, no blades involved, so the stencil can be made as small as you wish. When being used the stencil does not stick to the blade at all, in fact, it must be held in place with Scotch tape, so there is no distortion when it is removed.....

[Bob Warner]

I am going to toss out something here that may be so obvious that nobody is considering it. Could it be your bulb does not put out UV rays?

There are only a couple reasons to get a blank with no logo. At first I thought maybe the stencil was put on the wrong side of the stencil (not between the light and the stencil) but that would not be the problem due to how you explained your problem.

In lay mans terms the UV light "sets" the emulsion on the stencil when exposed to UV light. Developing washes away the unset material, leaving you with a white logo to etch through. So, no UV no "setting." You just wash the entire emulsion off leaving you with a white stencil.

I don't think over exposure is your problem because if your logo is very thin, you would just "set" the entire thing with your overexposing so you would not get ANY white to show up, it would all stay green.

Is it possible that there is a treatment on you picture frame preventing UV light to preserve pictures?

I say you are not getting UV light to the stencil, not sure why but that is my opinion.

[Wade Holloway]

I agree with Bob here. If I remember correctly if you over expose it then it would be black, clear or blank would mean under exposed. So I think Bob hit the nail on the head here with maybe your bulb does not put out any UV.

[pipecrafter]

UV is the key ingredient. If the bulb is "full spectrum", but doesn't put out UV, it won't expose the stencil. And not just any bulb will put out UV. Florescent lights do, to an extent. There are UV LED arrays, but they can be expensive. There are also bulbs sold to folks that have lizards and such that put out UV light.

This can devolve into a detailed discussion of spectral absorption properties of glass, radiative emission patterns of various materials, and the difference between UVA and UVB. I'm happy to go down that path if anyone is interested - but I suspect it would bore a great number of folks to tears.

The simplest method I've come up with is to sandwich my stencil material and transparency between a piece of black G10 and a piece of borosilicate glass clamped down with pony clamps. Then I expose it to direct sunlight for approximately 30 seconds and develop in total darkness using nothing more than tap water with a bit of washing soda in it (you could use baking soda). The washing soda reduces the surface tension of the water and allows it to get inside the mesh to dissolve the unexposed emulsion.

Some things to remember:
- Regular glass (soda glass) is not entirely UV transparent, borosilicate glass is. Some folks use thin pieces of soda glass with good results though, so YMMV.
- Florescent lamps are the most readily available source of UV light. So called "grow lights" put out quite a bit of it, but any compact florescent lamp will emit some.
- Get your stencil material and transparency completely flat.
- The UV light actually changes the emulsion on the stencil material from water soluble to water resistant, which is why the unexposed areas can be washed away with water.
- Direct sunlight is your best source of UV, but you can use other sources by increasing exposure time.
- Use high quality stencil material if your logo has lots of fine lines, otherwise you might not get the detail you want.

This page has some excellent info on it:
http://www.desiredcreations.com/howTo_TLPhotoEZ2.htm
Even though it's targeted for silkscreen folks, the process and procedures are identical to what you want to do.