Dancing again

Earlier this week in Another Dance? I posted about some new work, which was really my opportunity to finally finish something started back in 2008.  In that post I'd got as far as making some cardboard models - to be used for mould making.

Well this photo shows those cardboard models set up ready for casting in silicon. 

I've previously used gelflex for shallow relief casting - but think I may have been converted to two-part silicon.  It holds its shape better, isn't so bubbly and gives a harder, stronger final mould.  The one major drawback is the price - because silicon can't be melted and reused like gelflex.

The walls for the mould are slices from a drainpipe, and these have been sealed at the base with clay.  The blue sheets underneath the mould are sticky back plastic - to prevent the cardboard lifting away from the board.

Here you can see the three silicon moulds, ready for casting themselves. (In a delightful shade of mint green!)

Again, I've used sticky back plastic to keep the silicon from floating away.  But instead of drainpipe, the walls for these moulds are slices of postal tube. I varnished the inside with a quick layer of shellac - so that the plaster wouldn't weld itself to the card.


Once sealed with clay at the base, the silicon moulds were then ready to be cast in SRS glass (a plaster-based investment) - which I buy from Special Plasters in Birmingham.  This has the necessary additions to reduce the likelihood of the mould cracking and failing at high temperatures.

This photo shows the final investment moulds once they've been released from the cardboard tube - and had the silicon removed, of course! I then went on to make a second set of investment moulds.

Once I'd finished the moulds, I left them to air dry for a couple of days.  Then came the firing:

Here you can see the six moulds set up in the kiln ready for firing.  I cut six pieces of fibre board (specially designed to survive kiln temperatures), and  cut a hole in each with a pastry cutter.  It works...but don't use it for pastry afterwards!

The pieces of board are then placed on top of each mould, to support small earthenware plant pots - which hold the lead crystal casting glass.  Once the glass reaches casting temperature, the glass melts and drains through the hole in the bottom of the plant pot (and the hole in the board) directly into the mould.  

Because I'm working with geometric shapes, it is possible for me to calculate the volume of glass I require relatively accurately using mathematical formulae.  In this case, the formula for the volume of a cylinder (πr² x h).  I can then multiply the volume by the density of my glass, to work out the weight of glass required.  I usually use Gaffer Glass, which has a density of 3.6g/cc.  There are other ways to calculate how much glass you need which don't require as much (if any) Maths!  I clearly just need to torture myself..!  You then need to add a little extra "for the pot" - as not all the glass will manage to drain through.

This final shot shows the glass after firing and removing from the mould.  You can see at the edges that the glass isn't shiny where it has touched the mould.  It needs to be polished.  With lead crystal you have the possibility of using hydrofluoric acid to polish - though some smoothing with a diamond pad may be required first.  I don't work with the acid myself, but take my glass to a commercial crystal company who will dip small pieces.

Well that deals with the glass side of things - but I still haven't covered the laser cutting!  I'll have to do one more post later in the week... Bye for now!

Another Dance?

I made these two pieces (Dance) back in 2008.  They were two of several experiments I did combining concrete and glass. Unfortunately this particular brand and mix of concrete wasn't fully compatible...so after a few months some of the glass cracked.

But I've always wanted to revisit these pieces: I felt the design worked, even if the concrete:glass combo didn't.  I particularly like the fact that the pieces will stand (or gently rock...) on all four sides.

Well, the laser cutting course I did earlier this month finally gave me the impetus to have another go: as the laser can deal with both curves and circles accurately and efficiently!

My first job was to create the drawing files which would be used to control the laser cutter.  For this I used Inkscape - an open source vector graphics program, which you can download for free.  It's fairly user-friendly if you've used photo editing or 3D design programs - and there are plenty of videos on YouTube for beginners.  This is a screen shot of one of my files in Inkscape, showing some of the basic shapes. The pieces with the deep curves instead of circles will form a low relief on the front and back of each sculpture.

I also added a few extra shapes into the spaces on this worksheet (which I'll use to make moulds for another project) - as I didn't want to waste any of my plywood!


For the original, experimental Dance, I reused some old glass casts from a temporary sculpture.  This time round, I decided the pieces deserved some glass which was designed with them in mind!  In the past couple of months I've been working on a series of work called Shape Shifters - and I suspected that this style would carry across to my new Dance pieces.

So I started experimenting with cardboard circles...  This photo shows the final three cardboard models. (The circles were cut using a little plotter cutter - I'm not that good with a Stanley Knife!)  The orange/brown colour is down to a layer of shellac - which stops either the gelflex or the silicon welding to the surfaces when I make the moulds!  These are relatively low relief models (about 15mm), as I want the final glass pieces to be between 18 and 20mm to fit within the plywood framework.

I chose the diameter of the models to match the inside of a drainpipe, so I could use a drainpipe to form the mould walls.  (My foresight and planning are finally getting a little better..!)

I'll add another post later this week, covering the rest of the process.

Laser Cutting at Black Country Atelier

Lots to think about this weekend: yesterday I did the Introduction to Laser Cutting course with David Brannon at Black Country Atelier.

This photo shows my first experiments during the class. We used the open source vector graphic program Inkscape to create the drawings. These were then transferred into LaserWorks - the program which actually controls the laser.

By varying the speed and power of the laser, you can achieve different results: cutting or etching to different depths. (You can see two different etching depths in the 'Red' and the 'path' of Redpath)

Our test pieces were done in 3mm birch ply - but it's also possible to cut cardboard, leather, acrylic and even glass..! Different materials need different speed/power settings.

If you're based near Birmingham, I'd recommend Black Country Atelier. The course was a great taster - and once you've had the intro, you can book to use the laser cutter by the hour. I will definitely be visiting them soon!

Shape Shifters

I've been working on a new series of work in the past month - the Shape Shifters - and realised that it was about time I posted some background info (and images) on my blog!

The Walkers (Shape Shifters) Image: Simon Bruntnell

As usual with my work, they started life far from the kiln (and indeed the studio): on my living room floor.  While Francis reads the paper on Sunday, or we watch an old movie, I often sit on the floor with a cutting mat, some cardboard, and a Stanley knife (my favourite tool).  Footling about is what happens next - sometimes it goes somewhere, sometimes it doesn't.  That week I was messing about with concentric squares.

I started rotating/twisting the concentric squares - which gave a satisfying spiral.

That, of course, made me wonder about other geometric shapes - would I get a nice spiral with those too?  And at that point I resorted to some help from the computer.  (When I move beyond squares, I find that SketchUp achieves far better hexagons and pentagons than a pair of compasses and a protractor..! I can then print them out, and use them as cutting templates)

And you also get the chance to play with your shapes on the screen, to save your index finger from unnecessary cutting! The screen grab here, shows my pentagon templates all stacked up and rotated.

And the spirals worked well with the triangles and hexagons too.  So my Sunday afternoon at the cutting mat soon ran into Sunday evening...and Monday morning...as I cut out lots of geometric shapes. The photo on the left shows the triangular and pentagonal stacks.

These various stacks were then enclosed in boxes and varnished with Shellac, so that they could be cast.  My first casts (of the squares) were done in gelflex (middle photo).  But I  wasn't that pleased with the final result.  So I moved on to try a soft grade silicon (photo on the right).  It isn't as economic as gelflex - because it can't be reused.  But it is stronger (and seemed to give a sharper result too).

And these "positive" rubber moulds, I made the kiln moulds for the glass. Again, the silicon moulds produced the best results (so I've now made my square Shape Shifter mould in silicon too!) As you can see from Simon Bruntnell's photo of the test pieces, the first glass came out relatively well.  Please note that these have been coldworked (they aren't fresh from the kiln)!

Now I want to do some further work on the colours and the presentation. I'm thinking of casting the shapes in Jesmonite as well as glass - so that I can start building up some tessellations.