glue-chipping on concave glass

[BruceJackson]

Some time ago, I raised the question of glue-chipping on concave glass.
I wasn't sure whether I should do the kiln-work first or the glue-chipping and several people had comments which all helped clarify my opinion.

The client went ahead with the job and I thought I'd post this photo.

I decided to do the glue-chipping first, then had the glass slumped to the correct shape. The reason being that the firing isn't hot enough to alter the surface texture. If I had chipped after firing, the glue would tend to run towards the centre and I would have to wait for each letter to gel before moving onto the next letter.

The glass initially was cut with a flange (margin) of about 2" and slumped through a steel ring. This flange was later cut off leaving the oval of the correct size. Gilding and reverse painting was then done as per usual.

[Mike Jackson]

Hi Bruce,
Nice job! Thanks for coming back and posting it for us.

I am not sure if I will ever have one slumped, nor would I have any idea where to take one here in the Rocky Mountain West, but the information might come in handy someday. I would have always thought the curved glass would make it tough for screen printing or even stencils. Did you hand brush all the lettering and designs? The grape leaves would also take some reverse thinking unless you did those on decal paper and applied them. Just curious....

Also, Bruce, you might have a wealth of Signmaking 101 posts hidden in you if you ever have the time to share them. I made a bunch a few weeks ago but it appears not too many other readers here feel like posting them for the rest to see. You are certainly invited/challenged to make a few!

For the rest, Bruce has quite a bit of great information about numerous gold techniques on his site. Worth visiting! http://www.goldreverre.com

[Ron Berlier]

Hello Bruce,

A very nice glass piece! What is the overall size of of it?

I am surprised that putting the glass into a kiln to slump it did not change the chipped areas because of the high temperature. I suppose that if there were any changes they were to small to be noticed or of any significance. How long does the glass have to be in the kiln to get it to change shape?

I agree with with Mike about Signmaking 101 I'm sure you have a wealth of information that the forum community would be very intereted in knowing. If you have the time please consider sharing it.

Again, great job and thanks for sharing the completed job!

Ron

[BruceJackson]

Thanks for the comments.

Mike, It's been a while. Good to hear from you again. Thanks for keeping this forum going as well as theletterheads site.

I drop by occaisionally. I'm sure many people are in the same boat as me. The novelty of Internet use has long since worn off and I spend more time on other things than online. That doesn't mean I'm any less interested in the activities of others here.

I will give some thought to adding more posts. As you are aware, sometimes the same topics come around again and again when there's good information available in previous discussions.

Slumping the glass doesn't toughen it. The heating program we used brings it up slowly, holds it at 630 C for a while until it drops the right amount, then comes down just as slowly. The glass has time to cool evenly and reduces the internal stresses that cause toughening. The kiln time is around 8 hours.

It doesn't deform the surface at all. It's not hot enough for that. It is just as sharp and crisp in texture. The steel ring former is 2 plates of 5 or 6mm (1/4 inch) mild steel. We also used a layer of ceramic fibre between the glass and the steel to avoid direct contact. The top plate stops the glass from lifting at the edge, resulting in a flat margin and no extrusion marks on the edge from where it could slip through a little if it wasn't held down. The kiln work was done by a friend who does stained glass painting.

The size is 19" high, the convex is about 40mm (a bit over 1/1/2"). Enough to look nicely domed, although it really doesn't show in the photo.

All the work is hand-painted and gilded. I just drew it up on paper (yes, with a pencil!) and worked from that. The vine leaves are just fine line work with a little cross hatching for the first layer, following up with blended color to give it form.

I took photos at every step along the way with this job for the benefit of my client (who is in USA, while I'm in Australia). So I have a complete record for a step by step (except of the kiln in action).

If there was interest, I could make them available.

[Mike Jackson]

Bruce,
If the client doesn't mind, and if you have the time and energy, I am sure we'd all like to see the step-by-step process.

Mike Jackson

[Raymond Chapman]

What a great looking sign! Like Mike, I'm not sure that I would ever do a job of this type, but it is very interesting to hear of the process. As others, I would love to see the step-by-step photos.

Does anyone know where this might be done here in the states? And what does a process like this cost? (the slumping)

We are in the process of doing an oval glass job, but not this involved. We will try out Sarah's Angel Gild for the first time.

Great job Bruce.

[Mike Jackson]

Raymond,
Rick used to sell slumped glass ovals. I don't think they would fit in his small kiln, so he must have found a source for them. Pat Mackle might know. I didn't do a Google search, but I bet they are available.

I don't think chipping a domed piece of glass would be a problem at all. Angel Gilding one sound more tricky to me. Let us know how that turns out.

Mike Jackson

[Raymond Chapman]

I still have one of Rick's slumped oval glass pieces, but have never used it for anything. Like you I don't think he produced the pieces, but just bought them from someone else.

The job we have going now is an oval piece, but flat - so slumping.

[Mike Jackson]

Bump!
I just received a call from Steve Lainhart, asking about working on curved glass. He recently had a project needing silvering and lettering on a piece of conclave glass. Not only that, it was to be back lit. Anyway, I am bumping this to the top so he can find the thread. Maybe he will be able to post some on his experience.

Mike Jackson

[John Yarnell]

Wow this worked out perfect I just started a slumped glass piece also. I’m working on a finished size of 20â€x16†Just before Christmas Larry White called me and asked if I wanted to get together to work on some glass over the holidays. Larry asked me what I wanted to do for a project. I mentioned from the first time I saw a slumped oval I knew I had to try one. I asked around a bit and no one knew exactly where to go to find the glass. I looked around on ebay but did not find a piece I was happy with. I did a search on Google with some key words that people use on ebay (Slumped, Convex, Bubble) and found a good supplier fairly quickly. The company is called In Line Ovals. Within 10min and a little help from the lady on the phone my piece was on order. I received it two days before Christmas.
With this oval I wanted to try something new and challenging not that working on the slumped glass alone isn’t challenging enough. I wanted to try upside down deep acid etching on a slumped piece of glass. Now just so everyone knows Larry White is the man when it comes to working with acid and I probably wouldn’t get within 20ft of the stuff if he wasn’t right next to me. Larry has a great shop for working with chemicals like this and I really wouldn’t recommend keeping this stuff around unless you take the time to learn every safety precaution and use them. Acid is no joke. At one point in the project the stuff was smoking as it was eating the glass. I have some pictures of it.
I started off with taking a picture of my glass took it in to my computer and printed off a bunch of small ovals with the same curve to design in. I created some lettering that worked well on the curve of the oval scanned it back in to Corel so I could vectorize it. After that was done I sized it to my glass and cut out a mask in reverse. I knew that the oval would present a big problem with trapping air in the center so I designed around it. The only part of the piece that got the acid treatment was the lettering going around the perimeter of the oval. I applied the reverse mask and painted over it with asphaltum. After the asphaltum dried a pulled away my letters and that left the exposed glass to be etched. I painted the front side of the glass and we were ready for the acid bath. I built a open box just a few inches bigger than the oval to minimize on the amount of acid it took to submerge the glass as much as possible. We decided the box needed to have deep sides so we could tilt the bath up to let the maximum amount of air out from under the oval. If anyone wants to try this please call me or Larry and I we will describe in detail precautions we took to keep this project as safe a possible.
After the glass was submerged and burped I let it stay there for four hours it seems like a lot but I did some test pieces at a previous get-together at Larry’s and I had some positive results from a long bath in the acid. We pulled it out after the four hours had past rinsed it off and for the most part had a successful deep acid etch. The small trouble spot I had was from the remaining air bubble that clipped three letters at there base. It was really late at this point so I decided the best remedy was to paint asphaltum over the correctly etched areas and do a quick right side up acid etch on the missed areas. We stepped it up a notch and poured a small amount of undiluted acid on the area to save time and get at lest some texture so it wasn’t just clean glass. This is where the smoke came from. The glass does not have the same exact texture as the upside-down area but looks pretty good for a quick fix. Lastly I cleaned the asphaltum off the glass packed up thanked Larry for a great day and headed home.
I am now at the point where I’m ready to treat the glass. I will try to add some pictures of the day at Larry’s in the next day or two and insert them into this post. Thanks a thousand times again to Larry for all his help and guidance. Most of all don't try this at home unless you can take every precaution or Larry is there to walk you through it.

Thanks, John


Glass w/ vinly mask. Coated w/ asphaltum.


Glass in acid, air trapped under the center. Top portion of the A is etched, while the bottom is not due to the trapped air.


Glass rinsed, ready to be stripped. Final acid etched oval.

It's hard to capture in a photo, but in person this type of ecth looks very close to glue chipping without any frosting.

Edited to add photos.

Danny

[Mike Jackson]

Sounds like John and Larry already did the dislcaimers of working with acid...

For anyone interested, I can possibly explain the upside down etch "concept". According to Rick Glawson, when acid etching face up, the acid bath starts chewing away at the top surface of the exposed glass and gradually works its way down into more layers of glass. Unfortunately, the acid does not completely dissolve every bit of the glass product. It leaves small platelettes of microscopic glass. When working face up, the small platelettes settle back down into the etching area and eventually create an unwanted barrier between the unetched glass and the fresh acid.

So, reversing the issue, the glass is coated completely on both sides with asphaltum except for the etching areas, then placed face down into an acid bath, held off the bottom with a few spacers. The fresh acid begins dissolving the exposed glass, but this time the platelettes fall to the bottom of the vat, exposing new glass to new acid. This results in a deeper, faster, cleaner etch.

In many of the conclaves I attended, people were doing acid etching face up, using a red dye tinted acid bath. The edges of the glass had a folded masking tape "dam", sealed with parafin wax. I always cringed seeing all the acid projects all over the place, not to mention watching Rick pour acid onto glass wearing his sandals. Yikes! That process uses a lot of acid.

Again, keeping in mind that acid work is very dangerous, I would have suggested to John that he use the mica/acid sludge mixture on his concave project. Normally, it only takes 45 minutes to etch with the stronger acid mixture, and because you only need to mix up and cover the specific areas, it uses less acid. The "sludge" should stay in place on the concave glass, but if not, he could have done the project in maybe six or seven letters at a time. The same acid/mica mess could be scraped off, recharged with fresh acid and used on other letters. The mica etch also creates an interesting textured etch, vs the smooth etch of the bath. As John mentioned, the stronger acid gives off a strong, very toxic vapor, so extra caution is necessary.

Be careful!
Mike Jackson

[Larry White]

CAUTION, ACID ETCHING CAN BE A HAZARDOUS PROCESS. ENSURE FULL KNOWLEDGE OF PRODUCTS AND PROCESSES PRIOR TO USE. SEEK HANDS-ON INSTRUCTION WHENEVER POSSIBLE.

...mica etching produces that nice sparkly texture when water or solution gilded. It is the safest and most economical process. Leaving the mica on the glass longer than the recommended time is not a good idea as the resulting "silt" will reattach itself to the glass, causing the gild to be cloudy.

I typically refer to the process of using dilute liquid acid as "acid embossing". This can be done face up or face down.

On the face up method, weak acid for a longer time can leave the glass clear for a brilliant gild. Slightly stronger acid will leave a slight stipple which can produce a matte gild.

Face down, with strong acid, can emboss deeply depending on exposure time. It can also create an interesting ripple around the edges of the embossing. This rippling effect can be seen in many of the common production beer mirrors of today. The glass remains clear and has a brilliant gild.

The following link is to a MSDS for HF. Always know what you're working with and how to handle it safely.
http://walljewelry.com/TcMSDS.html

[John Yarnell]

Thanks Danny for adding my pictures to the post. I will try to keep you all updated as the project progresses.

John.

[Ingrid Mager]

Can I assume that three posts up (John Yarnell), the wrong pictures have been uploaded to the link?
They don't quite seem to make sense to me....
~Inga

[BruceJackson]

Hi Ingrid,

I think something must have changed over time. This post was 6 years old, but since you bumped it, I re-read it an see that my original images have disappeared too. I'll see if I can edit my original entry.

[Anthony Bennett]

I can see the original artwork now Bruce.
Amazing.
I would love to see that step by step you considered doing.