Stencil material question

[David Peterson]

I bought some stencil material from Martronics and I'm trying to figure out what I'm doing wrong. I was hoping you guys could help. I made my logo and used the photosensitive stencil material to get a logo built. I developed it the way they told me, but there's still a white silky material that sticks to the blue coating. Does this stay on and does it let the electolite through? Does it matter which side I use? I tried using the stencil on a spare piece of steel and it turned brown and melted everything when I turned the voltage on. I was using 5 second cycles and it still burned the material. Any ideas? Thanks.

-Dave
dave@sagebrushcountry.com

[Agletric]

Dave,

Just to check -- You did remove the thin celophane layer covering the Blue material, after exposing, right?

Dan <><

[MJ Hofbauer]

I don't know for a fact. But it sounds like the protective film was left on. This is a quote from Bob Warner's tutorial on the site.

Turn on your light and keep track of the length of exposure time (more about this later). After exposing is complete, turn off the light and remove the protective plastic coating that is on BOTH sides of the photo-resist material. Put you exposed stencil into the developer (more about this later also). After the stencil is developed, rinse it off in cool clear water and pat dry with lint free cloth.

-MJ

[Bob Warner]

Could also be that you did not expose long enough or that you developed too long (or too strong).

It takes a while and some trial and error to get it right. It all depends on your light, your time, your logo and how well it blocks light, and developing.

Just make little logo's on about 1" square stencils and change things up until you get what you like, then make a bigger one the way you want it to be.

[David Peterson]

I remember taking the plastic layer off both sides. It looks like the white silk layer may intentionally be there, but I don't know.
Here's a picture from their website, and it looks just like mine did except it's not Wilson.


Is the logo supposed to be completely see-through and only show air in the text? Is the blue material AND the white supposed to develop away? I guess my problem is that I have no frame of reference. Thanks for helping guys.

-Dave
dave@sagebrushcountry.com

[fitzo]

Dave, factory stencils have a mesh sandwiched in the middle. The thread count of the mesh determines to a large extent how crisp the etches come out. I would think your "home-developed" materials would still need something in the center of the sandwich.

Stencil based electroetching will get warm, and you can overheat it to where it'll burn the stencil. I personally use "strike" times of 1-2 seconds at most, then wait 3-5 seconds between strikes. 5 seconds sounds a bit long to me.

I did a review of stencil materials some time back (see Supply section if interested), and did find that some were more "transparent" than others to the current, and needed lesser strike times to avoid rapid overheating.

What, BTW, are you using to supply the current, and are you using commercial electrolytes matched to your steel type?

[Bob Warner]

The stencil material is nothing more than a piece of silk that has emulsion (firm blue jello) on both sides. Then there is a plastic cover on top of the emulsion to protect it.

When you expose, you are allowing the ultraviolet light change the composition of the emulsion, firming it up. Then you develop and all of the emulsion that was no exposed to the light will wash away. Your stencil should be blue with your logo showing. The logo should be white silk showing. Not yellow or slightly blue tint but completely white. The rest of the stencil is dark blue.

Your logo should look exactly like the logo you used to block the light. If you have an "O" in your logo, you should have blue around the outside and a little blue dot in the middle. The "O" should be white silk.

The etchant is put onto the pad and the electricity passes through the silk part ONLY and etches the metal. The blue part of the stencil will block the flow of current on the blue areas.

The result is your etching through the silk and leaving your mark on the metal.

Clear as MUD?

[PS_Bond]

Hmm. I wonder what I'd get if I mounted a small piece of silk in a rigid frame, sprayed it with PCB photoresist, exposed and developed it? Project for the next couple of weeks, perhaps...

The thing that immediately springs to mind involves trying to get the unexposed resist out of the silk. Still, could be interesting.

Peter

[Bob Warner]

Peter,
Sounds to me like you would have your own screen printing business.

[David Peterson]

The lights finally came on . I get it now. Thanks for the great info. I'm going to try it again this weekend and see what happens. Should be fun at least.

-Dave
dave@sagebrushcountry.com

[PS_Bond]

Originally posted by Bob Warner
Sounds to me like you would have your own screen printing business.

Whether it is a good use of my time is another matter entirely. Still, it fits with my usual attitude on these things - how best to find out how cost-effective it is for me to do this stuff myself...

At least I have all the materials on-hand.

Peter