Heat Work and Degree of Slump

 Searching for a Relationship in Heat Work in the Slumping Range. 

Now I know why so little research is published that indicates a lack of any positive results.  It is disheartening.  There is no pointer to other methods or relationships.  It is difficult to pick yourself up and try something different.

Yes, this means that my testing for a relationship between time and temperature and degree of deformation was unsuccessful.  With the means at my disposal the relationship between viscosity, heat work (time and temperature) and the degree of deformation is either too complex for my equipment, methods, or concepts.  I found no formulaic relationship between time and heat to get the same amount of deformation, due (I believe) to the factor of viscosity.  And I have no way to measure viscosity.

Some things did become apparent (many of them already known)

Holding time constant and increasing the temperature results in greater deformation.  Nothing new in that.  Holding the temperature constant and increasing the time results in more deformation.  No general relationship could be determined.  But at 650C changing the time from 15 minutes to 45 minutes resulted in an almost linear increase in the proportion of deformation, but a decreasing proportion from 35 to 55 minutes, although generally regular from 15 to 35 minutes.

There is a mild relationship in the amount of deformation between increasing time between 640C and 670C, but this breaks down at 630C and below, where increasing time does not “counteract” the lower temperature.  My speculation is that the viscosity is too high below 630C to maintain that (very mild) relationship. 

Top blue line is the temperature times 10; orange line is the temperature; the others are the thicknesses.

There is a relationship at a given temperature with the proportion of deformation within each thickness.

 

This graph shows increasing time at 650C.  The 12mm thick test piece has a relatively regular change throughout the time range of 15 minutes to 45 minutes.   The 6mm and 9mm pieces show similar proportional changes up to 35-minute soaks, but then drop as the time continues to increase.  This is weird and requires further investigation to see if it is an experimental bias or something else.

At the best, this writing up of my failures, has led me to renewing my tests of deformation by controlling for time and for temperature separately.  The first of the new tests is in the kiln now.

Sink

The big aperture drop for the Willow Tea Rooms has been good experience for smaller projects.

I am in the process of helping to create an oval sink with a specific height, and dimensions at the top.  Rather than creating a custom mould, it was decided to do a free drop to the desired height with a flat bottom to the sink.

View from above of the slumped blank

An aperture in the desired shape was cut from a 25mm thick board and suspended on bricks at the correct height.  

The set up for the glass

It was set to fire and the person came in the evening to check on progress and advanced to the cooling when the desired amount of glass had touched down to the shelf.

Sink from the end

The flat excess glass was cut away with a tile saw. and then the polishing began.

trimmed and roughed edge

There is quite a bit more grinding to be done to get to the polish stage and then there will be the drilling of the drain for the plumbing fittings.  Only a few weeks until completion.

Weary

This is the title of a piece that has been a long time in reaching completion.  

The word "Weary" seems to me to encapsulate the feeling toward the end of any pregnancy.  The tipped over stance encapsulates that feeling for me.  

I have now finished the piece and put it on a plinth ready for exhibition.

Lighting Covers

I have been asked to provide two dozen diffusing light covers for an auditorium.

I've finally got the mould sorted.

This has involved getting an existing cover to take a mould from.  The refactory fibre paper used to make the mould was soaked in hardener and formed around the master.  I left it to dry for a week while I went on holiday, but it was still damp when I came back. I had to remove all the weight packing the fibre to the master and let it air dry for days.  When it could support itself, I put it into the kiln to fully dry and cure.

It came out of the kiln firm, but it needed sanding to final shaping and to smooth the surface.

This is the mould sanded, hardened a second time and now washed with a separator to keep the glass from sticking to the mould.  The advantage to this kind of mould is that it is light weight and reasonably easy to shape and adapt to a number of simple shapes.  Its big disadvantage is that it is pretty fragile. Also it is not cheap. 

The tests have been made for the diameter of the discs and the temperature required for an appropriate slump.

These are the two test pieces together with the original piece.  Now I'm ready to produce two of these a day for the next week.

Verrier

Verrier specialises in the design and making of architectural and decorative glass for domestic, and commercial settings. Leaded and kiln formed techniques are used to provide windows, wall hangings and decorative features.

Verrier uses the traditional values of high quality craftsmanship, attention to detail and fitting the work to the requirements of the client. It is preferred to visit the site to ensure the glass is suitable for the situation. Clients are also encouraged to visit the studio to confirm the work practices and ability of Verrier to meet their requirements.

Restoration of existing windows is done to high standards whether for simple or historically important windows. Verrier has worked with the Glasgow City Heritage Trust on several projects and with various architects and builders on larger projects.

Verrier also conducts weekend workshops and some evening classes, as well as supplying glass and tools to other workers and enthusiasts.

Verrier is run by Stephen Richard who has had art training at the University of Kansas and Glasgow Metropolitan, and in master classes with Paul San Casciani and Klaus Moje. He is involved with various professional bodies: Past Chairman of the Scottish Glass Society, Past Chairman of the International Guild of Glass Artists (currently on the advisory board), Past Chair of craftscotland, member of British Society of Master Glass Painters, and the Contemporary Glass Society. He established Architectural Glass Artists in 1998, which has grown into the largest collaborative glass studio in Scotland.

More information is available in my cv (link at the top of the page) which links to various projects.
You can also contact Verrier:

email at stephen.richard43@gmail.com

telephone at 0141 556 5700

mobile 0771 883 1117

or drop into the studio:

Studio 8 WASPS Studios, 77 Hanson Street, Glasgow G31 2HF

Domes

During the week I created a shaped top for a dome.

This is 550mm in diameter and is 90mm high. The rim will be cut to fit the opening on site.

This shows the great flexibility of glass. This was done in clear glass, but can be done in any coloured glass. The method used allows a completely unmarked dome to be made. When looking through it, there are no distortions.

I am now asked to make another in etched and painted glass for the same client. This will be for a much more decorative part of the house.

For those interested here is a bit on how this dome was made.

The specification was for a 550mm diameter dome shaped piece with a height of 90mm. To do this I cut the required diameter hole from 10mm ceramic fibre board of 700mm square. I lightly sanded the edges of the hole and fired the piece in the kiln to remove the binders.

I then suspended the board on an circle of kiln bricks, looking rather like Stonehenge, but without the lintels. I placed the board on top and centred the 3mm float glass over the hole. I then fired at 250C/hr to 620C. It took a little over two hours at 620C for it to complete its slump to 90mm. Had the glass been thicker, it would have achieved its drop more quickly.