Making iron pipe...2000 years ago

[jlpservicesinc]

39 minutes ago, gmshedd said:

jlpservicesinc, thank you adding to the conversation. I added some comments that may, or may not, be of interest, beneath your comments above. Do you remember the name of museum where the Egyptian items were displayed?

It was the MFA in Boston..    

I find early tools to be very interesting and probably why I remember the tube..  Really I find anything including hand labor to be interesting all throughout time including today..  But, find I like to be physically engaged with doing vs looking or reading about it.. 

Nice you have found interest in the history..  It can be very much fun to fantasize about things were done..  I still romanticize about how clean and simple things used to be..  

 

[gmshedd]

Thanks for the MFA info. I'll check to see what they have.

[ThomasPowers]

Have any of you checked the melting point of copper vs the working temperature of glass?---and remember that structural strength generally plummets as you approach melting temps!

However doing the most general of research: Wikipedia, under Glassblowing, mentions "Researchers at the Toledo Museum of Art attempted to reconstruct the ancient free-blowing technique by using clay blowpipes. The result proved that short clay blowpipes of about 30–60 cm (12–24 in) facilitate free-blowing because they are simple to handle and to manipulate and can be re-used several times." citing:  Stern, E.M. & B. Schlick-Nolte (1994). Early Glass of the Ancient World 1600 BC – AD 50. Ernesto Wolf Collection. Verlag Gerd Hatje: Ostfildern.

The bibliography for that section looks very interesting and citing a number of academic journals in archeology, chemistry,  etc; with the "Journal of Glass Studies" being a heavily cited source.

Though a short blowpipe sounds like a recipe for "glass blowers cataracts" to me...of course many occupational hazards were common in the old days---fire gilding anyone?

[gmshedd]

6 hours ago, ThomasPowers said:

Have any of you checked the melting point of copper vs the working temperature of glass?---and remember that structural strength generally plummets as you approach melting temps!

Yes, the melting point of copper is 1984F, and the working temperature of glass at the consistency of honey is about 2130F (that's the temperature they use at the glass shops I'm familiar with). Another reason to switch to iron pipe.

However doing the most general of research: Wikipedia, under Glassblowing, mentions "Researchers at the Toledo Museum of Art attempted to reconstruct the ancient free-blowing technique by using clay blowpipes. The result proved that short clay blowpipes of about 30–60 cm (12–24 in) facilitate free-blowing because they are simple to handle and to manipulate and can be re-used several times." citing:  Stern, E.M. & B. Schlick-Nolte (1994). Early Glass of the Ancient World 1600 BC – AD 50. Ernesto Wolf Collection. Verlag Gerd Hatje: Ostfildern.

The bibliography for that section looks very interesting and citing a number of academic journals in archeology, chemistry,  etc; with the "Journal of Glass Studies" being a heavily cited source.

I bought that book (used) last week for $10, and I looked up E. M. Stern's J Glass article that includes the discussion of clay blowpipes, too. She obviously wasn't convinced that the first glassblowers immediately started using iron blowpipes, but I would like to ask her what she thinks now--her book and journal article are both from about 1993-94. There could have been some new archaeological discoveries in the decades since then.

6 hours ago, ThomasPowers said:

 

 

[jlpservicesinc]

The glass touching the metal is not fully molten as soon as it touches the pipe it cools and sticks to it..  If the object is made quickly enough it would mean little in terms of temperature or one verses the other as melting temperatures vary in terms of how long something is exposed. Did they have huge ovens like they use today to blow glass?  I don't know..  If they had a small crucible with molten glass in it I can see where it would be possible to do.. But hey..  

With that said, maybe I am completely wrong as again it was just a vague memory and not a study in glass blowing..   Thats okay too as maybe there was an insert or something.. i just remember the copper pipe with green glass which was fractured on the end of it.. 
 

The only reason I remember it was I was intrigued and surprised it was copper.. 

[ThomasPowers]

I remember a wood fired glass furnace I saw in Action around 50 years ago near Jamestown VA; blowing green bottle glass, Looked large to me.  (Rehder in "The Mastery and Uses of Fire in Antiquity" mentions glass crucibles being fairly small in the earlier times though having multiples in the same furnace was known in medieval times.

[TWISTEDWILLOW]

Sorry to wake up an old thread, it was an interesting read

I was wondering if anyone here has ever incorporated glass blowing in with their metal work?

[jlpservicesinc]

I had looked into it for some finials of large twisted baskets..  

I never pressed forwards because of the extra expense..  The project was a donation. 

Still have not finished the finials.. 

[Frosty]

I slump bright red glass frit into the center of spread crosses. The guy at the art glass supply insisted it couldn't work even after I showed one to him. I bought a tube of different color "noodles" and use chips to accent things. Molten glass is about as sticky and stringy as it gets, the front of my forge looks like a pyrospider lives in it. 

Frosty The Lucky.

[TWISTEDWILLOW]

JLP I could definitely understand that, I wouldn’t buy any tools or materials for a freebie either! 

Jerry

that sounds awesome do you have any pictures?

[Irondragon Forge ClayWorks]

Glass blowing is still alive here in the Ozarks. Silver Dollar City in Branson MO has two resident glass blowers. If I remember right (haven't been there in years) they have two or three ovens and a couple of assistants. They do custom requests. If interested Google Silver Dollar City glass blowers.

[TWISTEDWILLOW]

It’s 6-7 years since I’ve been to silver dollar city last time but they still had the glass blowers then,

IIRC during the demo the lady was saying it took like 2 days to slowly and safely shut down the furnaces without damage, 

On another note they have all kinds rusty old tools and machines dotted through out the park,

while walking around I saw a massive! ginormous! screw press half the size of my shop building setting out in a flower bed just rusting away un noticed

made me wanna ask if the park would sell it! Lol

[Frosty]

An early one, I got better at both crosses and slumping frit but I forget to take pics. 

Frosty The Lucky.

[TWISTEDWILLOW]

That’s awesome Jerry!

Did you do that using a gasser or solid fuel forge? 

You got me wanting to try that on my split crosses!

[Frosty]

The gasser, I don't burn solid fuel at home. Well rarely, very . 

The real trick is keeping it from flowing out through the bottom of the cross and coating the other side in a curdled globbery mess or hopelessly cementing it to what it's laying on. Soap stone works petty well, I picked up a couple tiles at the local tile shop. 

Let us know if you come up with a way to keep the glass where you want it. The one pictured is barely slumped and didn't fill the corners of the negative space. However get it much hotter and the glass goes everywhere. 

Some shapes are easier to fill than others, the negative space in a spread cross is one of the more difficult. In my limited experience that is. 

Frosty The Lucky.

[TWISTEDWILLOW]

Ive never melted glass before and I don’t have a gas forge but I’ll give it a shot! 

I think that would look great on some of my crosses! Thanks for the idea

[Latticino]

Sorry to have somehow missed this whole thread and not contributed earlier.  Lots to process.

To start, let me correct some misunderstandings.  While I did get a job offer from Corning to work there as an engineer on their process line right out of undergrad, I didn't take that offer.  I wanted to stay in the Boston area, and yes there was a woman involved.  Years later I got into glassblowing full time, received an MFA from the School for American Craftsmen at RIT, and ran my own glass studio for around 10 years.  I have also taken a handful of classes at the Corning Studio with some glass masters, but I was never employed there.

I am far from a glass historian, but I do have a bit of practical experience with both glass and steel, mostly separately.  I've blown glass with both steel and stainless steel pipes, and the latter are significantly easier to use.  Modern glassblowing pipes are usually tubes with a spun, swaged or plastic insert mouthpiece and a welded, drilled, bar stock end for picking up glass. This helps with both heat transfer and weight.  The “business end” of the pipe needs to stay hot so thermal shock doesn’t spall the glass right off the end of the pipe, so in use we typically preheat that end to just under red hot before attempting to “gather” glass from the furnace, and keep it at elevated temperatures during the entire process.  Needless to say it is important for the end you are holding and blowing into to be cooler.  The extra thermal mass at the business end stays hot longer.

Thermal shock at the glass/metal interface in this case is a product of the different thermal expansion rates of glass and metal.  I’d have to check to be sure, but I can say from experience that copper bonds better to molten soda/lime/silica glass (and causes less thermal stress in the glass after annealing) than steel.  Of course each glass formula has slightly different thermal characteristics.  In my experience encapsulating steel within molten glass is a recipe for thermal shock and eventual cracking, sometimes violently, of the glass.  Of course I have mostly worked with “hard” soda/lime/silica glass, not “soft” borosilicate glass (like torch workers). 

These days there are different custom glass formulas that bond better with steel, but I haven’t any experience with them.  I know that shortly before he closed up his shop, Al Paley was conducting same fairly extensive experiments with Corning to come up with a formula that would be more compatible with his forgings.  Side note: I did blow a handful of glass lamp shades for his shop back in the day, but these were cold connected.

Please note that no matter how good a glass/steel bond looks it can be very subject to thermal shock down the road.  With the glass surrounded by steel it may be better than having the steel surrounded by glass, but in either case very slow annealing after the glass casting would be prudent (8+ hours down from 900 deg. F to room temperature for glass thickness around ¼” is what I remember; a computer controlled annealing oven is a good idea).  I’d also remove any sharp corners from the steel that impact on the glass.  Ideally I would do a check for stress in the glass after a test full process was done using a polariscope, but those work best with clear glass.

[anvil]

I have limited experience with glass and iron. I did some glass in a punched eye as finials in handled tools. I used glass bottles I found and crushed the glass to a fine powder. The powder went in the punched hole and all was heated on the top of my forge on a preheated 1\2" plate until the glass melted and fused. I then "packed" the glass into the void to fill the space and slow cooled the whole deal to prevent thermal shock. I covered the plate and glass unit with thermal blanket and buried it in lime. The bottles were common so the colors were brown, green and clear. The idea for this came from "The art of the Blacksmith" by Alex Bealer. note": I just gave a quick look thru his book, but did not locate the article. I'm still pretty sure it came from there or perhaps one of Weiger's books.

I also worked with a glass blower who ordered basically trivet shapes from me. Three riveted legs and varying shaped tops forge welded from rectangular stock. He wanted my hand work as forged detail to accent his glass. He then slumped the glass into the open top. The height of the legs varied per piece and I believe he sold them as glass and iron planter pots. I saw some of the finished units, but do not know what his techniques were.

[JHCC]

I'm pretty sure that's in Bealer, not Weygers; I'll check later. 

[anvil]

Lol, thanks for the spellcheck...  

[Frosty]

I remember it from "Art of Blacksmithing," too. 

Frosty The Lucky.

[JHCC]

On 4/13/2022 at 1:00 PM, anvil said:

The idea for this came from "The art of the Blacksmith" by Alex Bealer. note": I just gave a quick look thru his book, but did not locate the article.

Found it: it’s on pp. 303-4. 

[anvil]

Thats the article. Thanks for finding it. 

[JHCC]

Knowledge is not diminished by being shared!

[anvil]

absolutely