Slip Casting

I was anxious to try a bit of slip casting in the drop moulds we made last week.  Sadly, the moulds were not completely dry as I found out when I poured the slip into one of them.  It took far too long to set and the results weren't pretty.  Undeterred, I found some small moulds on a shelf in the studio and tried my hand at pouring two vessels which I joined and decorated with some coloured slip work.  Perhaps I've found my calling in designing.....

Slip work just out of the moulds

Finished work

...bathroom sinks! 

Drop Mould

Another day in the Plaster Studio making a one-piece or drop mould for slip-casting.  The first step was covering my models  - pink plastic drinking cup and a glass - with mould-grease.  I filled the plastic cup with wet clay and placed it upside down on the bench and put the cottles in place with a coil of clay on the outside to prevent leakage.  For the glass, I placed it on a clay slab and pressed into the clay before pushing the cottles into the clay.   I then made up a bucket of plaster and poured around and over my models.  When the plaster was set, a shot of air released the model from the mould.

I am set for slip casting next week.  How will I decorate the surface?  I have some research to do before then.

Waiting for the plaster to set in formwork

Slip - Slab - Cracks

Oh dear, cracks have appeared in my slip slab forms, on the base.  I have made new forms today and have taken steps to avoid previous mistakes, such as :  drying on newspaper, thinner bases, scoring and slipping and covering with plastic wrap as the forms dry.  I will find out tomorrow if my efforts are successful.

Today we also made up another 25 kg of clay into slip for yet more slab work and future slip-casting.  I now have a design in mind and a plan for production.

Two sisters reading

My Two Sisters Reading figures are finished and drying.  When they are bisque-fired, I will apply oxides and under glazes.  I was not satisfied with the larger form, as pictured in a previous post.  I made alterations to the position of the head so the figure looks downward as if reading, the disembodied hand belonging to the other younger sister sharing the moment.

Slip Cast Slabwork

This week I've been working in the Glazing Studio making forms from slip-cast slabs.  Wednesday and Thursday were full of frustrations but by Friday, some of my forms were behaving and I felt more confident with the process.

The work began with making the slip from casting powder.  This was a messy and dusty process whereby 25 kg of casting powder was added to water in a large plastic bin.  This was mixed with an industrial size 'stick blender', then sieved.  We added black, blue and yellow to three separate containers.  Previously we had poured our plaster slabs in readiness for this work.  

We made patterns on the plaster slab by painting, slip trailing, dripping, sponging, etc. with the coloured slips.   The un-coloured slip was poured over this to form a slab.  The slabs took approximately 30 minutes to set.  They could then be peeled back and flipped over to reveal the pattern, much like flipping a crepe.  The slab is now ready for formwork.  After much experimentation, I found cutting simple curves or squarish shapes worked best.  By joining curves, squares or rectangles, it was possible to make a vessel into which wet slip was poured to form the base.  Timing is everything.  Too dry, the slab would crack and too wet, it would not support itself.

In the photo, you can see my forms with poured bases drying on the plaster slab.