the second pour and de-mold

We learned so much from the first pour and we were determined to make sure the second and final cement pour went well. We had some additional challenges with the pour in that the school year was quickly coming to a close and Jasmine had professional commitments looming.  We also had to wait for the benches to cure in 30 days before they could be sealed with a protective concrete sealant. All of this needed to be done technically before the contract expired, at the end of June. Based on our tight scheduling constraints, we decided to pour on Tuesday and then de-mold on the Friday, May 17th the last Professional Development Day of the year.  This meant that the second de-molding day would sadly not have students present.  At this point however, we felt the process had been celebrated and the important learning had been achieved.  The actual molds would not be altered in any way, so that part would not be a surprise to the students.  We wanted a second crack at the perfection of the visual ideas, not to recreate the entire project.

We did need a crew to help and our incredible grounds and maintenance staff stepped up and came to our aid.  They were fantastic in that they came in strong numbers and cheerfully flipped, unbolted and lifted the final pieces in the rain. I can't say how thankful we were to them for their help.  The results were truly fantastic - the second time was the charm!

So what did we do differently? First of all we allowed an extra day for the pieces to solidify along with the daily watering.  The weather was cooler and wetter this week which helped our cause.  Jasmine took all that she had learned from the various experts consulted and hung the rebar without the use of the wooden planks across.  The theory was that the wood prevented the cement underneath from drying at the same speed as the concrete surrounding it, causing the cracking. She also worked carefully to push the concrete into all the nooks and crannies in the book stack mold to avoid those pesky bubbles. She also gave the side of the mold a couple of whacks with a rubber mallet to agitate any remaining bubbles away from the edges and up to the surface.

We all held our breath when the de-molding began. What we found cheered us beyond belief.  Everything was better.  The detail was better.  The bubbles in the book stacks were greatly diminished. Even the pop can came out intact (Jasmine cut it out this time to be sure).  And best and most importantly of all, there was not a single crack to be found.  Each and every bench was perfectly structurally intact. Now all we had to do was wait for the cement to cure and be sealed. After that, we could get to the work of installation.

De-molding Day

 Wow! So much has happened so quickly and time has flown by!  Let's begin with our de-molding day. Two days after the pour we were ready to take off the mother mold and release the cast concrete underneath.  We were careful to keep the concrete moist and protected from the elements so that there were no sudden changes in humidity/temperature while we waited for the big day.  The Richmond News offered to come to help us document this exciting part of the process.  You can find a link to their story at http://www.richmond-news.com/Richmond+students+create+with+school+mind/8363275/story.html

Our students, Jasmine and a crew from our grounds and maintenance team worked tirelessly for hours to remove the molds and reveal the cement underneath.  The process involved first sliding the molds off of the sand and onto a wooden board.  Then many hands worked to flip the heavy piece so that we could access the hard outer shell and begin the process of unbolting it.  After all the hardware was removed, Jasmine used a chisel to separate the hard pieces and reveal the softer pink rubber mold underneath. Next Jasmine carefully peeled the inner mold off to reveal the detailed, now concrete, objects underneath.  We then cleaned and reassembled the molds so that we could potentially make more benches.  We quickly covered each piece with burlap sacks and sprayed them with a hose to help further protect the concrete from cracking.

 Unfortunately, we discovered that there was cracking already.  We were unsure of the extent and the reason for the damage, but as we continued to release each mold it was clear there was a problem with the concrete setting around the rebar suspension system. Looking at the images you can see fissures appear at the same spot on each bench which gave us our first clue. They each appear right above where the clamps, wooden pieces and wire were placed to keep the heavy rebar - commonly used in cement to add extra strength - from falling to the bottom of the mold (see previous post).  It did not dampen the day for us as the cracks were not wide, the pieces seemed solid and we thought we could simply reinforce the benches to make them work at this point.  There were some more minor issues with tiny air bubbles in the book stacks and the pop can did not come out in one piece, but we felt we could deal with these things. Just seeing each bench revealed was like magic.  It still took our breath away to see how clear objects like the banana or the gum wrapper came out.

After the initial joy of the day passed, we had to reflect on what the reality of the cracking meant.  The benches could not be counted on to stand up over time or function properly.  With our cold winters it would mean that water could easily get into the cracks and freeze, turning our beautiful benches into rubble in no time.  Jasmine was understandably not comfortable with delivering less than perfect pieces and after all the hard work and learning we all desperately wanted this project to end happily.  So we were incredibly relieved when the City of Richmond Public Art Program said they would cover the cost of a second pour as our budget had run dry.  It was a generous solution to a difficult situation.  Jasmine launched a thorough review of the first process and consulted additional industry experts so they could pinpoint the reason for the cracks and how we could avoid them in the second pour.  We really thought we had allowed for every possible variable through our first intensive consultation and planning process from the first pour, but as so often happens in art, something unexpected happens. We were so very lucky to have a second chance to get it right, and we were not going to waste it.

The Cement Pour

So the day has arrived when we are finally casting our molds.  Our morning began by unwrapping our molds and clearing them of any moisture and sand that may have accumulated.  Jasmine checked again that the molds were level and we kept a sharp eye out for the truck. Jasmine sprayed the molds with a release agent to help with the de-molding. The students could only observe at this stage for practical and safety reasons as the PH level of the particular concrete mix we used was 11.  Jasmine, the concrete company employees and our concrete techs were in charge of the pour.  The concrete was tinted to add visual interest and difference to the traditional cement benches that will  be installed. As the concrete was poured in, Jasmine tapped the sides of the molds to release any air bubbles that might be lurking in the mix and potentially take away detail.   Once the concrete was in place, it was smoothed and left to partially set up.  When the surface was firm enough, we covered the forms with burlap sacks and wet them in order to keep an even level of moisture as the concrete set.  When we were done, we wrapped them up in a tarp to keep them dark and poly sheeting to protect them from the elements.

Prepping the molds

We have prepped the molds!  Jasmine brought the molds to our school so that we could get them ready for the pour the next day.  We helped her unload the van and the materials/equipment we would need and brought the molds into an art room that didn't have a class in it at the moment.  The students then proceeded to clean the molds with damp cloths: a meticulous job that ensures nothing will interfere with the detail we hope to get with the concrete. They then tightened the bolts on the mother mold ensuring it was ready to support the weight of the cement. Students cut burlap into wide strips that will eventually be used to keep our freshly poured concrete moist.  Meanwhile, Jasmine's sandbox was built and filled with sand - thank you to our fabulous maintenance and grounds staff!  We put the sandbox in the fenced area behind the technology education rooms as planned and walked over the molds.  Jasmine had previously tested the molds to see what we would get and below is an example of the incredible detail from the "lunch" locker designs.

 Next Jasmine and her crew began the task of suspending rebar inside the molds for extra strength. They used wires, clamps and wood to keep the rebar steady and away from an edge.  Next we moved the molds to the sandbox and then began the delicate job of ensuring they were level.  Afterwards we used the shop vac to clean out any sand that got into the molds in the process and covered the molds for the night.

We were all excited to see what would happen in the morning.  The cement truck was scheduled for first thing and we were as ready as we could be.

Preparations for the big cement pour continues...

So we are now in the final stages of the plan for the pour.  We only have one shot at getting it right so we are trying to allow for all possibilities and make sure responsibilities are clear and timing is in place.  We have been able to use a cage area behind our Technical Education Department that is concrete, fairly flat, and most importantly a fenced and secure area for us to cast our molds. I recently met with Don Landy from our District Maintenance and Operations Department regarding what help the school district could provide.  Don was incredibly supportive and offered many helpful suggestions and a crew to assist.  I continue to be ever thankful that everyone involved is such a positive force in this project.  Jasmine suggested a sandbox to keep the molds perfectly level.  Here is a simple drawing of what she wanted:

Don volunteered his crew to help with this and improved on the design by suggesting thicker and taller boards he had available at the yard.  He even had sand that could be reused at the end of the project for another project as nothing will be mixed or spilled into the mixture to spoil it.  The sand is simply a leveling compound.  A flurry of emails and meetings has resulted in the following simple list of events as described by Jasmine:

Tuesday April 30^th, 2013  Prep Day

            Don and crew build sand box and fill it with sand. Canopy installed?

1.     Rinse rubber molds in sinks in the art rooms

2.     Pat Dry with Paper Towel

3.     Ensure that all bolts and wing nuts are very tight (using pliers) on the mother molds.

4.     Return the rubber molds to the mother molds

5.     Put molds in garbage bags and tape the plastic bag tight around the mold

6.     Put molds in the sand

7.     Cut openings in the plastic bags to reveal mold (access to mold) but keep the mother molds covered in plastic to prevent moisture damage. (weakens the mother mold)

8.     Jasmine to install rebar hanging structure in molds

9.     Level molds with sand, leaving sides as exposed as possible to tap with hammer to eliminate air bubbles during pouring

10. Cover with plastic

11. Weight the plastic

Wednesday May 1^st

1.     8:00-8:30 Jasmine Ensure molds are dust-free, spray with mold-release

2.     8:30-9:00 molds release sets

3.     9:00 Lafarge arrives with truck, technician mixes cement with chemical to catalyze the concrete, Contech Concrete technicians arrive

4.     Approx 9:30-10:00 Contech concrete pours concrete into molds

5.     Jasmine stands by to release air bubbles with hammer and/or stirring deeper shapes (tin can, container)

6.     11:00 Pouring is complete, Contech will finish the concrete surface

7.     When concrete is hard enough soak cloth with water and place on top of hardened concrete.

8.     Cover in plastic and weight plastic.

Thursday May 2^nd

1.              AM hose the fabric on top of the concrete and re-cover with plastic

2.              Noon—check fabric/moisture. Adding too much water to the concrete will not damage the concrete curing as per Lafarge’s advice.

3.              4:00-5:00pm (end of the day) Add more water to keep moist over night

Friday May 3^rd

1.              9:00am Jasmine arrives to de-mold.

2.              Remove plastic and wet cloths.

3.              Prepare dollies and wood for lifting (Jasmine to explain)

4.              Turn the first mold over so that the mother mold is facing up…remove all nuts and bolts, keeping the group together.

5.              Jasmine will use chisels and hammers to pry open the first section of the mother, repeating the process until the mother mold is removed.

6.              Students to group and put the mother mold back together using the letters A-A, B-B etc…

7.              Jasmine to remove rubber mold and return to the mother mold.

8.              Slide the cast bench on to 2x4 supports.

9.              6 people lift wood supports with bench on it, on to the dolly.

Repeat until all casts are de-molded.         

 Students will be a key part of every part of this process where appropriate.  We have a crew signed up to help out whenever appropriate with the key days being the mold prep day and the demolding day.  It has been a long road to this point, and it does not seem real that we are finally here.

Local Publicity

We were recently contacted by the Richmond Review in regards to an article on the Hugh McRoberts Public Art Project they were covering.  Specifically they were covering the official endorsement of the project by Richmond City Hall.  Unfortunately this meeting occurred over spring break so we were unable to supply them with a student or teacher perspective.  However, The Richmond Review has kindly offered to cover the story of our cement pour and demolding.  We are so pleased to have them share in this exciting process.  Here is a link to the first article:

http://bit.ly/116Fvls.

Casting the lockers and objects

Here are some images of the change room lockers and the objects placed on top of them for casting.  The beauty of the casting portion is that we can cast almost anything using a similar compound to the "mini locker" exercise the students participated in previously.   All of these images were taken by Jasmine in her studio.  We decided since the compound required to cast such a large surface had some levels of toxicity (unlike the mini locker compound which was non-toxic) that this portion ought to be completed without students present and with the proper safety equipment in the studio. Jasmine was careful to keep to student ideas in combination with her own designs.  We now have funding for a potential 6 benches.  The two benches featured here are the lunch and book benches.  The books came from our art department in the form of collected cast offs and the lunch was Jasmine's selection.

Notice the incredible detail here on the books - including the embossed text on the spine.  The sandwich stuck to the casting material, however now inedible, will be forever remembered in concrete in perfect detail.  Once the initial mold is made of the exterior (pink part), then the mother mold is cast to strengthen the outer layer (white part).

We are now preparing for concrete casting day.  Jasmine has spent a fair amount of time researching what kind of concrete to use and how best to cast our design with longevity and structural integrity in mind.  One detail different from the original design is that all benches will be cast in the same tinted colour as opposed to each being a different colour. Through industry experts, Jasmine discovered it was not practical nor effective to try and hand tint the concrete ourselves on such a large scale.  As such, when the concrete truck arrives on site it will contain a uniformly coloured - the vote was for yellow - concrete material. Jasmine has researched coloured sealants that will also do the double duty of protecting the benches and enhancing the colour intensity.  We have not ruled out spot colour (i.e. tinting the object a different colour so it will stand out).  Skala has designed benches for the rest of the space that will be simple, elegant and smooth rectangular grey concrete forms - a perfect foil for our pop of colour and texture.

We are now at the point where we will are planning the details of the pour and demold on school property.  We do not yet have a confirmed pour date, but it will be soon.  Stay tuned!