Tony That is very strange. I'm no chemist, but he only thing I can think of would be that there is a chemical reaction going on between the ferric chloride and the dry film resist and/or the stopping out varnish which creates a substance that is much more corrosive than ferric chloride. Therefore everything underneath this chemical is eaten away. This might also explain why the resist lifts after several hours.
There might be someway to put this odd phenomenon to good use to create a sundial face if you could reverse your stencils somehow to be "negative" images. John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Tony Moss" <[EMAIL PROTECTED]> To: "Sundial Mail List" <[email protected]> Sent: Tuesday, April 08, 2003 4:36 AM Subject: Positively negative results! > Hi all, > I have been etching, photo-etching and engraving copper, brass and > bronze for 30+ years now so those processes hold very few surprises for > me. > Until now I have always had stainless steel etched by subcontrators, > mainly because the mordants usually recommended seem much more hazardous > than the ferric chloride I normally use on the copper based alloys. > > My recent experiments using just ferric chloride alone to etch stainless > steel have revealed a puzzling phenomenon on which I would welcome > comment. The material was prepared as for non-ferrous etching and a > commercial dry-film 'resist' applied in the usual was. On exposure to > the ferric chloride nothing seems to happen for hours but then it becomes > apparent that the resist has lifted to reveal that the resist protected > areas have etched quite deeply whereas the areas exposed to the mordant > all along are untouched and 'as new' i.e. the reverse of what should have > happened. The areas which should have etched away are left as shiny > plateaux and the areas which should have been untouched have been > attacked. > > The experiment was repeated using stopping out varnish as a resist but > the same thing happened. It seems to defy logic but I have to believe > the evidence of my own eyes. > > What is going wrong here? > > Tony Moss > Lindisfarne Sundials > > > > > - > -
