nice texture

[Roderick Treece]

I found this web site while doing a search for sandblasted water textures.It appeares to be chipped but it might also be deep carved first.What do you guy's think?

Roderick
http://www.conradschmitt.com/CaseStudies/nwcstl.asp

(link edited by administrator to make it shorter) MJ

[Larry White]

Face down acid embossing... probably done in China, I mean am I close?...am I right? ...Milwaukee? ... What do you think Pat?

-Larry

[Robare Novou]

Yes, it was acid etched upsidedown. No, it was not done in China. It was done in the acid room of Conrad Schmitt Studios, Located in New Berlin, Wisconsin...a suburb in the Milwaukee area.

[Mike Jackson]

The additional textures and variations in the etch may have been assisted with tempera colors. I never tried it, but Rick explained it to me. The protected areas are masked as normal. Then a layer or two of tempera colors are painted into the open areas, thicker in some areas. The front of the glass also gets protected prior to emmersing the entire glass etched side down, but held off the bottom of the tray with some blocks placed in the protected areas. The acid gradually starts dissolving the tempera colors, exposing areas to the etch sooner than others and thus deeper etch. I'd expect there would also be some paint additives that might make the tempera paint dissolve more slowly or randomly. Face down etching allows the fine particles to drop to the bottom of the tray, exposing new glass to new, fresh acid.

With face up etching, the particles can eventually build a barrier that keeps fresh acid from getting to new glass.

Caution: Acid Etching is Very Dangerous. Follow all precautions and refer to the documentation regarding hazardous materials.

Mike Jackson

[Sarah King]

Thanks for the explanation, Mike, very interesting. Do you think any tempra paint would work or is there one kind/brand that is better for this than another? It sure is a neat trick.

[Mike Jackson]

Sarah,
I really doubt it matters much which brand would be best, especially considering they were doing the process 100 years ago. They probably used ground pigments and mixed their own tempera colors. I think the key is a thick, almost gummy paint, carried in a water based medium that would dry fast, but also redissolve with water. I am sure there are better quality tempera colors: the cheapest K-Mart hobby/kid variety vs something like RichArt. Prang used to make middle of the road tempera.

MannBrothers sells a lot of different kinds of paints, probably to fill the movie set needs in California.
http://www.mannbrothers.com/products/pa ... themes.htm

I'd probably check Hobby Lobby, Michaels, or any good art supply store in your area and try out whatever they sell. I am sure Dick Blick sells a good brand of tempera, too. I am sure I have the formula for mixing tempera here in one of my old sign books, but I doubt that would be necessary. Half the fun is experimenting with whatever is in front of you anyway.

With kids around the house and shop, we never did much full emmersion baths in acid. Most of the time we just used the sludge mixture of acid and mica flakes which pretty much stayed put and was fairly cost effective.

Still, I believe the tempera technique was the one used in the smaller design on that web page. The other one with the cranes or egrits looks more like it was glue chipped to me. I don't believe the piece in the upper left is a detail shot of the one in the lower right.

Mike Jackson

Here's the info from their web site:

Conrad Schmitt Studios, Inc.
2405 S. 162nd St.
New Berlin, Wisconsin 53151
The Studio is located 14 miles west of Milwaukee.
Phone: 1-800-969-3033
1-262-786-3030
Fax: 1-262-786-9036
E-mail studio@conradschmitt.com

[Mike Jackson]

If you are thinking about working with acid, read this first!

Material Safety Data Sheet for Hydroflouric Acid:
https://fscimage.fishersci.com/msds/11171.htm

Mike Jackson

[Patrick Mackle]

Face down acid embossing... probably done in China, I mean am I close?...am I right? ...Milwaukee? ... What do you think Pat?

-Larry

Yes sir, definatley acid etched face down right here in the US. I'm a little surprised to learn that they use asphaltum as the resist, I would think they might also use computer cut vinyl. Its really no big deal to do this etching, you just have to commit to do it and pay for the proper equipment and deal with the proper large scale disposal issues. One etcher I know of side steps that issue by contributing his sludge to a concrete company that uses it in their mix.
In all my years of searching out acid information I do not recall mthe term "leptat", however a google search brought up a few along with stained glass info. I actually saw tons of this type of glass being imported from Spain a few years ago and oddly enough it reaqlly doesn't do much for me as far as eye candy. After you have seen it done on a mass produced scale it sort of cheapens the effect some how. To me it is far more intriqueing to see this face down acid technique in a pub sign or antique glass lamp globe. Seeing it on several large arcitechtual glass church panels just does't have the same reverence ...am I right?
On the other hand there does seem to be a market for the process, and a rather lucrative market at that, judging by Conrad's digs, churchs and hospitals and other funded customers are able to afford these higher priced products.
Seeing this interest would intice me to offer the same product, I love the effect of embossed glass, but have always been put back by customers that faulter at the price. Maybe better customers would support this leptat product. It would be great to begin on a small scale and up size as the panel sizes increase. May mean leaving California and buying a ghost town, am I right Blake??
Pat

[Larry White]

Ahhh... that does have a certain appeal! Fresh air, tumble weeds, just the smell of some familiar acid. The sound of something other than your own shaddow....and some good friends.

[Robare Novou]

Leptat, pronounced Lep-tat, was developed and patented by Conrad Schmitt Studios. I saw the patent, it used to hang on a wall of one of the office hallways. I can't remember the year of the patent, I suppose I could go look it up, best I can recall is around 1959, but thats just a guess.
Seems to me, I had read about upsidedown acid etching in books that were much older than 1959. I also heard rumors of it being the formula of someone else, that never patented it.

Conrad Schmitt uses 70% hydroflouric acid, cut with a certain percentage of water.

The front side of the glass is just sealed with 3mil vinyl masking, (so Im told). I seem to remember them rolling on the asphaltum, letting it dry, and then putting on the protective vinyl mask. (thats what I would do)

The sides are given two coats of asphaltum along with the design on the back. Prior to the asphaltum application on the back, a computer cut vinyl mask is put down and the non acid etched areas of vinyl are peeled away, leaving clear glass, this clear glass is then coated with two coats of asphaltum, left to dry for two or three days, after which the remaining vinyl is pulled from the back of the glass, exposing that which is to be acted upon by the acid. I should mention that removing of the asphaltum covered vinyl does not always go smoothly, there is a certain amount of touching up of jagged areas.
It is at this point that a sea sponge is dipped into asphaltum, and then dabbed onto the exposed areas of the glass design. I never saw them use tempra paint, although I dont know why you couldnt.

The acid room is about 400 sq. ft., with a huge rectangular tank in the middle, large enough to lay 4'x8' size sheets of glass into. Its always a two man operation, (for safety reasons). The men wear protective rubber boots, suits, shoulder length rubber gloves and enclosed headgear with respirators. A huge exhaust hood hovers over the tank and is turned on prior to the workers entering the room. The lid covering the tank is removed and the Large Glass is carfully submerged facedown into the tank, and left there from 30 minutes to an hour, depending on the stregth of the acid. After handling the glass in the acid, the workers hose off with fresh water.

After the allotted time, the glass is removed and hosed off in the acid room, the glass is then transported to the rinse room, where the protective vinyl is removed, and then placed into an upright vat containing a mineral spirit like liquid. The glass is left in this vat for a day or two, upon emerging from the vat...all asphaltum has now dissolved off. It is then recleaned, dryed, and inspected. If all is ok, the glass panels are packed and shipped to the job site, where Conrad Schmitt workers will install them.

I only worked there for about a year, I had volunteered for working in the acid room.
I was told nobody had ever asked to work the acid room before (so I guess that means I was crazy).
You had to be there longer then a year to be picked for the acid room, and from what I was told, some guys hated it, while others didnt mind it. Whats more dangerous?, working with acid or working around a woodchipper?

They do have colorful folders containing pictures and info on this product, drop them a line and ask for some literature.

[Patrick Mackle]

Entertaining to hear your account of how they did their etching. Also 70% hf is difficult to obtain anymore in my experience.
I wonder if they make their own or buy it around 51% and increase the % themselves.
Your post reminds me of all the acid etching experiments I did long ago trying to learn and duplicate antique glass pieces I found in stores, museums, books and such. I used Contact paper, pariffin, beeswax, animal fat, tars, varnishes, lead foils and even a thin level bead of water as guards to protect the glass from the acid and its fumes. I tried all froms of commercial etching resists and hung out at the local college in the plate making class hoping to find something called Senderfelders asphaltum resist, touted to be THE BEST acid resist. When I finally found a crumpled old can and tried it, I saw the resist lift off and float to the surface after only seven minutes in the acid- heartbreak!! and another dead end!
I traveled to England to locate Embossers Black or Brunswick Black as it is referred to in Duthies book "Decorative Glass Processes" I found some in the UK but even the shops that used it told me that they would add red lead oxide to make it hold up better to the acid, and that even then it was necessary to retouch the lost areas. I don't know how they EVER were able to do 3 tone etching with that Brunswick n if it won't hold up to one acid etch and a rinse. I spent too much time retouching everything.
In your post you mention the soaking in mineral spirits to remove the resist. It reminded me of how messy that step was in my one car garage. I devised more ingenious ways to recycle rags, filter solvent, and generally try to economize on sludge. I remember being good at taking the resist off with razor blades in its dry state.
Also because with the face down method you are removing alot of glass which settles to the bottom as fine sand, there comes a time when you need to clean the pan. That sand combined with the flouric crystals is a pretty hard sediment.

It sounds like they are still having problems with their asphaltum resist. I don't know whether they mix it themselves or buy it ready made. I never was happy with anything I was able to buy. I did, over the years collect and research old time scribblings and mentionings in old books, but none seemed worth pursueing. Some sounded downright misleading. One early one called for Pink Dragons Blood and another for something like "elephant rosin". Many years later I found the solution to Dragons Blood in an old plate makers journal as simply being made by placing a stick of "red sealing wax" (used to simply melt onto and seal a written letter) into a sock or bag and pound it into pink dust with a hammer. Any search for "Elephant rosin" went out the window there after. I guess I sort of gave up and figured that all my endeavers to find something that would hold up to acid on glass and hold the detail that is seen on those old 3 tone acid embossed antique panels was lost forever, being taken to the grave by those old craftsmen who held their trade secrets so dear.
Last year I was approached to remake some acid etched gas light globe for the original 1902 Montana State Capitol Building.
That job had originally come to me 25 years earlier when I was still in a one car garage. I had done a sample back then and was told I had the job, but it never happened. I found out 25 years later that they had lost the funding. Anyway the job called for asplaltum paper transfers to be made and applied to the globes for acid etching. I tried several commercail resists hoping that by now something would be available that would work well. Nothing I purchased worked well enough to match the detail on the original 1902 globes.
I decided to try and mix a resist from scratch, based on all the years of searching for that one formula that must have been used by those old english embossers. It had to be low tech, no UV base, acrylics and plastisols were out of the question. Most importantly it would have to withstand more than one etch if it was to achieve at least a two tone etch, let alone three. And if that wasn't hard enough, it would need to be tranferable via paper or gellatin to a round glass globe. I rummaged through old boxes, some thin and yellowed, still containing dust and marks from my old garage 25 years ago. I went to Home Depot a got a gallon can of wet patch. Back at the shop I poured out some of the wet roofing patch and proceeded to select some of the old additives I had collected so long ago to enhance the commercial resists. Within a week I had fine tuned a mixture that held up to the acid better and longer than anything ready made, and it was transferable. I screen printed it onto a dissolvable membrane.
After rubbing the transfer to the globe, the way they were done originally, the membrane was dissolved, leaving a perfect asphalt resist of the 1902 Montana State Seal on the globes, which were then acid etched. I still have a little of that resist in an old sauce pan out back in the shop, covered with an old piece of glass. I think I could mix it up again. I don't get much call for acid etching, not as much as I would like. But I wonder if those people at Conrad might be interested in trying my resist. It could be brushed or screen printed.
I took pictures of the globe etching job. Maybe someone could help me put them up for viewing. That job was a challenge and it was fun to hold and study an original globe, for hours at a time sometimes, and think about how it was decorated and by what sort of personalities, all those years ago.
Pat

[Larry White]

Hey Pat, can I just follow you around for a few years?

[Robin Sharrard]

Wow, what an interesting post! A big thanks to everyone for taking the time to post their stories, experiances, and tips. I've only done the emersion process a few times, once at Larry's and a couple of times here at the shop. What kind of apperatous does it take to handle a heavy 4' x 8' piece of glass over a large vat of HF. I get nervous just placing a small piece in the little tank I have. I always lift the glass (when trying to get any trapped air out from under the glass) away from me cause I have this fear that the tabs I placed on the glass for lifting might let go then I've got this big splash of acid all over everything. Robin

[Mike Jackson]

Robare,
That seems like a stretch for the Patent office to grant a patent for something people had been doing a long time. Right! I don't see much new in their patent. People had been using asphaltum for a long time as a resist, and simply "sponging" on more asphaltum doesn't sound like much new (going back thousands of years). Maybe the patent office looked more at the specifics of elements like 70% hydroflouric acid, timing, and equipment.

Thanks for posting the information about your first hand experiences. You've been quiet for a long time. Nice to see you posting again.

Pat, thanks to you, too...as always.

Mike Jackson