Tuesday, February 21, 2017

hai-chi: eutetctic inlay

Right before I left Milwaukee, a local Metalsmith named Hai-Chi Jihn enrolled in my summer course on Drawing for Digital Fabrication. Hai-Chi had previously taught at Cardinal Stritch University in Milwaukee and so I had been aware of her and her work since first arriving in Milwaukee. That said, we had only met once at an opening. After spending four weeks in the course with Hai-Chi, I have to admit that I was so bummed that we had not met early. Simply put, Hai-Chi is a wonderful human being. I don't believe I have ever met such a hard worker and such a kind and thoughtful soul. I was so sad for the course I was teaching to be over as I knew is marked the end of having daily conversation with Hai-Chi.

During the course, Hai-Chi shared her method for making amazing inlay pieces. Check out the following images.

Note registration marks for applying PNP paper (resist) to both sides of the brass shim stock.

A view of the brass shim stock from McMaster Carr.

Brass after etching using ferric nitrate. (note Hai-Chi has cut a section of this piece out for use in an object she created)

Amazing detail in the images of the etch above.

Here the brass is fused (not soldered) to the silver by taking advantage of the eutectic melting point.

The two photos above show the sheet after it has been run through a rolling mill. The metal pattern distorts slightly but further imbeds the brass into the silver creating a single sheet.

Above you see objects fabricated from the sheet. In this case we are viewing some hollow constructed forms.

This process takes advantage of the eutectic melting point when silver and brass are brought together and heated. The melting temperature of these two metals is lowered when they are touching each other. The word "eutectic" comes from Greek and means "easily melted". The eutectic melting points of silver, copper and zinc (the metals present when soldering silver to brass). The melting point of a copper / silver / zinc alloy is significantly lower than the the melting point for each individual metal, this is why zinc is used in silver solder (if you want to "make silver solder" you can melt a bit of brass with your silver). 

What happens on heating is that the solder at the joint melts first and alloys with the metals either side of it (which is required for a strong bond), however, with these two metals, the alloying process does not stop there - the reaction runs away with itself as the metal at the joint alloys up into the silver. This run away alloying and melting is why you never put silver next to brass when you laminate a mokume gane billet.

A big thanks to Hai-Chi for taking my class and for allowing me to post the images of her work! I've been showing this to my Intro students and they have been amazed by her work.


Nick Carter said...

Beautiful! I need to try something similar with the CNC rather than etching.

Frankie Flood said...

Yes, Nick! That would be cool!