Upside Down Mica Acid

[Ingrid Mager]

On another forum, somebody made reference to UPSIDE DOWN ACID/MICA ETCHING, and mentioned that he thought that gum arabic was involved.
So far I am having trouble locating anything about MICA/ACID process done upside down either here or on a web wide search. Could somebody be kind enough to point me in the right direction to read about it or clue me in?

Thank you,
Inga

[Patrick Mackle]

Inga,
Upside down etching and mica etching are two different things leading to two different effects. Even if you used gum arabic to initially hold the mica to the glass, it would dissolve and release the mica in an upside down position.
In antique glass signs, I have only seem upside down etching in relatively small pieces, and usually in clear plate glass that was then mirrored.
Where did you read your account? It seems like a novice's statement or a misunderstanding.
Pat

[Ingrid Mager]

Inga,
Upside down etching and mica etching are two different things leading to two different effects.

Well, YES, of course!

Even if you used gum arabic to initially hold the mica to the glass, it would dissolve and release the mica in an upside down position.

Exactly. It only stands to reason and that is what I posted back...but what do I know.

In antique glass signs, I have only seem upside down etching in relatively small pieces, and usually in clear plate glass that was then mirrored.

Where did you read your account? It seems like a novice's statement or a misunderstanding.

It was a post from another forum. We rather got into it with the Gum Arabic and all, so I thought I had best come here and get it cleared up.
~Inga

[Larry White]

I've typically refered to the mica process as "acid etching", and the face down style of acid work as "acid embossing".

Face down acid embossing is a bit tricky. It's done in a vat of liquid acid, which requires appropriate handling techniques. The larger the piece, the more difficult it becomes. Basically the glass is placed in the vat, stood off from the bottom of the vat at least 1/4". Acid is then added to the vat until it reaches the top of the sides of the glass. the panel is then carefully lifted and relowered to (hopefully) force any air bubbles out. As opposed to acid etching, the glass can be left in the acid for a longer time as the byproduct of the etching falls away from the glass and deposits on the bottom of the vat. The open areas of glass that are to be embossed can also have a "pattern" applied to them. I've used tempera paint. The acid will start eating away the exposed glass, then the painted pattern will fatigue and fall away, expossing that portion of the glass to be attacked by the acid, and leaving the the desired pattern.

I would suggest mastering mica etching first. Then if you want to try some acid embossing, start with some small test pieces using a small vat. Always be very careful when pouring off the acid from the vat into it's storage container!!

The HF is never used at full strength. It is always diluted. There are some pictures of this process in a step-by-step I did here:
Rick Glawson Sign



The letter boarder on this initial plate was 2 staged acid embossed. The "dots" were embossed first, then a second pass embossing was done on the border. As the border was etched, the dots also etched deeper. This was a test piece for this sign,






-WB



.

[Ingrid Mager]

[quote="Larry White"]I've typically refered to the mica process as "acid etching", and the face down style of acid work as "acid embossing".

Face down acid embossing is a bit tricky. It's done in a vat of liquid acid, which requires appropriate handling techniques. The larger the piece, the more difficult it becomes. Basically the glass is placed in the vat, stood off from the bottom of the vat at least 1/4". Acid is then added to the vat until it reaches the top of the sides of the glass. the panel is then carefully lifted and relowered to (hopefully) force any air bubbles out. As opposed to acid etching, the glass can be left in the acid for a longer time as the by product of the etching falls away from the glass and deposits on the bottom of the vat. The open areas of glass that are to be embossed can also have a "pattern" applied to them. I've used tempera paint. The acid will start eating away the exposed glass, then the painted pattern will fatigue and fall away, expossing that portion of the glass to be attacked by the acid, and leaving the the desired pattern.

Yes and I have been scouring this forum reading all I could find about that from when you posted back in 2005, or even earlier.

I would suggest mastering mica etching first.

It seems much easeir and safer, AND I really love the surface rendered by it!
I am getting a glass cutting lathe this week and hope to soon be sharing my first tests with both, so you can all have a good laugh watching me bumble along. AH-ahahahah. Maybe I will even have some good luck with it all.

Then if you want to try some acid embossing, start with some small test pieces using a small vat. Always be very careful when pouring off the acid from the vat into it's storage container!!

Good idea.....pretty much what I was guessing. Guess I better invest in a pair of sandals...is there a special Glawson Model I should be looking for?

So far,I have been pouring over all of the posts from here and other places and have quite a stack of info, but nothing is like actually doing it. (Thank you so very much!)

The letter boarder on this initial plate was 2 staged acid embossed. The "dots" were embossed first, then a second pass embossing was done on the border. As the border was etched, the dots also etched deeper. This was a test piece for this sign,



Cool.....very nice.
----------

This still leaves the mystery of what FACE DOWN MICA ETCHING process that uses gum arabic is.......

~Inga

[Patrick Mackle]

The only reasons I can see for the gum arabic step would be:
*to allow for the use of a smaller quantity of mica flakes (less waste) as the mixture could be poured off and discarded.
*it may have given a sharper image of the flakes in the glass, owing to the fact that they were held in place a few minutes longer.
*the fact that MANY panels could be prepared and stored ahead of time, ready for the etching room.
*on overly large panels, it would be a sure way to distribute the flakes more evenly, and keep them from washing away when the acid was poured on.
Getting bunches of flakes to flow out means having to jiggle the panel about- a very difficult move on a large panel containing acid.
I think that covers it.

As I see it AND have experienced it, the whole point of etching face down is to allow the eroded glass to rain away from the surface. In doing this, greater depth is achieved as will as a clearer/brighter etch. It also creates a series of minute rippled "veins" along the edge of the etching areas.
These look really great when the glass is gilded or silvered.
Mica etching on the other hand uses the mica flakes evenly deposited on the glass as a loose sort of resist that inhibits the etching action and in turn leaves an imprint of the mica flakes in an even mottled pattern in the glass. Mica etching is generally quite shallow in depth, however I have noted deeper bites where a second application was applied. Mica etching has been done in the past both on clear glass, AND also on glass which has been frosted, either by white acid, or grinding with emery powder. Lead foil was used as the resist method on these earlier panels.

From time to time I want remind readers that you must be well informed with the safety procedures when working with hazardous materials for the safety of yourself and anyone in your area.
Pat

[Danny Baronian]

'This still leaves the mystery of what FACE DOWN MICA ETCHING process that uses gum arabic is.......'

Inga,

to my knowledge there is no such thing. The only time I've seen gum arabic used was by Haden, a friend of Dave Smith's when he came over to the first Memorial Conclave. He'd brought a sample that he brushed on gum arabic in an uneven manner, then submerged gum abraic down in acid. I guess you could add mica, but as the gum abraic was dissolved, the mica would drop off, yielding nothing more than you'd get with the gum abraic.

The result was a very nice texture that could be best described as the look of beach sand after the tide went out, an undulating, bumpy, clear texture.

The acid worked through the thinner parts of gum to the glass, and eventually eliminated the gum arabic in it's entirety, as Larry's description of using tempra.

This type of treatment would be best used when the piece remains clear, no paint or gild.

[Mike Jackson]

...and, if doing upside down etching, you would normally cover the front and edges with several coats of asphaltum. Only the etched areas would be exposed to the acid.

I never did this process because of the potential danger and the cost of the acid necessary to fill an appropriately sized vat. With mica, you only need a small amount of acid. Mica is relatively cheap, too.

Be careful! Before you handle the acid, be sure to read the specs and have safety gear and neutralizing solutions ready.

Mike Jackson

[Ingrid Mager]

Thank you Pat, for your astute synopsis. You are almost like an alchemist in my book!
I will lay to rest this desire to know more about this mystery (?) process for now...maybe you even hit all the points, Pat.
But if anybody has some more information about this technique, I would love to hear about it

~Inga

Well, now I see that Mr. Baronian has added to this topic and I am most appreciative of all this input. I was up until nearly 2:00 AM (with an early morning wake-up ahead of me) because I was pulling my hair out trying to find information on this subject.

I am keenly interested in clear glass looks/surfaces, and so this is of interest, now that I know what it is, but in all honesty, Mike, I do intend to stick with just mica acid for starters. Who knows, I may never take it further but once it was mentioned, I just HAD to know.

Thanks a bundle, guys,
Inga

[Doug Bernhardt]

Just a quick addition from someone who never really messes around with HF for the reasons Mike describes.....BUT, Smitty (still on vacation) showed me his results with a process with tempra paint much as described and the irregular rate at which the "dis-ruptor" drops off into the vat creates wonderful effects. Everything is worth a test/try but safety first!!