Saturday, May 18, 2013

Proprietary Problems

In this post I wrote about my gap filling tests. I decided to go with the resin/mortar combination. I ordered some resin from Screw-fix because it is relatively cheap and because I had spoken with a structural engineer last summer and he had recommended it. The problem is, it comes in a proprietary tube that doesn't fit in a regular caulking gun. I had already decided that I would make a custom tool to help me apply it to the bricks, but I never imagined the tool would require so much effort to make.
Here's what I've come up with. It is based on the same principle as the clay extruder I made last fall. 

The first problem was the extreme amount of pressure that is applied to the pieces. Initially, the notches on the vertical post were pieces that I attached with screws, but the force of the bar was ripping them out. So instead, I notched out the post itself. As well, the plate where the tube rests had to be re-anchored with extra support. 

The second problem was the shape of the resin tube.
It has a stem in the middle that doesn't slide. So I needed an extruding stick that was tube-shaped. Luckily, the workshop has a bunch of random bits and pieces, so I found a PVC pipe. I thought I had this working well, but then I noticed that the resin wasn't mixing properly. Normally, there is a white resin and a black hardener and they mix in the nozzle to produce a grey substance. I wasn't getting any of the hardener. I puzzled over this for a while until I realized that there is another sliding part inside the stem. My extruding stick needed to have two parts- a tube-shaped part for the outside, and a rod for the inside.
The workshop pulled through again. I found a smaller PVC pipe and a cable tightener that I could jam in the end. Above is the assembly: the small tube goes inside the big tube and all the parts are threaded onto the bolt.
It still takes a lot of strength to pull down on the bar. I have to keep reminding myself to hold it closer to the end because I can really feel the mechanical advantage with a longer lever arm. My hand just keeps sliding down because I want to see how the resin is coming out onto the brick.
The Screw-fix resin is relatively cheap, but their proprietary gun costs £30 (when a normal caulking gun is under £5). They know that anyone who buys their products will also have to buy their tools. I think I've managed to thwart their plans...for now.


Friday, May 17, 2013

On constructing solo

It's hard being the only person working on this project. Physically, it means a lot of redundant work- going up and down the ladder, going back and forth from the workshop, going in circles trying to find that darn jigsaw that I had a moment ago...Mentally, it's stressful, because there no one else to blame when things aren't going right. I'm only half joking. I am accountable to myself, fully and entirely. I feel like I push myself farther when I am alone, for that reason, but I also feel the weight of every action in my mind.

At a recent thesis defense where the defendant presented a beautiful timber framed "Oneiric Hut", one of the panelist's comments was that he was guilty of "the sin of pride": not asking for help, wanting it to be his alone. But even he had help- he had his wife as a partner throughout the building process. That is the best kind of help, a partnership where everyone is equally committed to the project. To just ask for outside help occasionally is difficult, because the helpers do not know the thought process and simply just don't care as much. I can't justify making someone trek across the field just to fetch and carry things and wait while I figure out what it is exactly that I'm doing. It's not fair to them and puts pressure on me as the leader.

So, I'm stuck going solo. Another difficulty of this is documenting the process. I can't ever really do 'candid' shots. I can pose and pretend, but I am the one who has to set up the tripod and turn on the camera, even when my hands are full of clay (a very annoying procedure). Below are some shots of me manoeuvring the roof formwork into position. I haven't put on all the "rafters" because  1) it would be heavy and 2) because I am working from the point backwards, and I need to be able to reach all the rows I'm working on.

I'm wearing my new bright blue coverall. It will get dirty soon...






Wednesday, May 15, 2013

Flintstones

It is impossible to understand the clay here without knowing about flint. I am surprised I haven't posted about it before. Actually, the weather has been dismal for the past few days, and I am just waiting to be able to start construction again.

The flint comes in rounded nodules of very bizarre shapes. They are whitish on the outside, although it is very rare to find one that hasn't been chipped. Inside, they are translucent purple.

Many of the houses around here are made of brick with an infill of 'knapped flint'- they cover the facade with a layer of render and then embed the flint, cut side out (the knapped side).

The workshop and cottage of Grymsdyke Farm are made in this way. They are older than the main house.

On one of my walks I saw two houses side by side, both of which were red brick and flint. One was built in 1893, the other in 2001. They looked so similar it was uncanny. Normally new houses have something that betrays their newness. But the randomness of the flint placement and the pre-weathered bricks allowed for an absolute continuity of aesthetic. Is this desirable? It does reinforce the distinct character of this area, but I wonder if there are other ways of building with flint that have yet to be discovered. The challenge is that it is very hard and stubbornly non-rectilinear.

Tuesday, May 14, 2013

Slips

I thought I would share another project that is going on at the farm right now. The kitchen is being renovated and as part of that project, Ed and Kate are slip casting custom tiles for a backsplash. Slip casting is an interesting process. It takes advantage of the viscosity and adherence of a liquid clay mixture. Liquid slip is poured into a mold so that it coats all sides, and then the excess is poured out.

The molds they've made are in two parts and are cast from a special hydrophilic plaster that absorbs the moisture from the clay. Below you can see the mold, with the hole for pouring the slip.


The originals were milled from a high-density model foam on the CNC machine. The motion of the tool bit is what creates the corrugations on the surface. One thing Ed said was that if they turned up the speed of the bit, it produced a wobble that was quite human in its imperfection. It's an interesting concept to consider- the fact that the actions of the machine are registered as an aesthetic, but then that these mechanical actions are programmed to have a human-like effect. It's almost contradictory. What is more valued, the hand-made imperfection or the robotic precision? Either way, the tiles are quite beautiful.



Monday, May 13, 2013

Sideways

Joining bricks horizontally is difficult. Well, actually, cleanly joining bricks horizontally is difficult. Is it a tool problem? Is it a material problem? Is it simply a silly thing to attempt?

I know from experience that mortar falls off the brick when it is turned sideways. Unless the mortar is really wet, and then it gets sloppy. So, I thought of using a two-step process: first, join the bricks with something really sticky, like resin. Then, pack mortar in from the top, using the resin as a base. The trial I made, though, is still very messy on the bottom.


The underside of the test piece. The resin is uneven and the mortar is showing through in some places.
Here you can see the resin on the bottom and the mortar on top.

I decided to try using plaster as the adhesive.
I thought I could trowel it on accurately, but it was still really messy.
Then I thought that if I had a surface against which I could wipe the trowel, it might produce a sharper edge. I modelled the overlap of the bricks (which is a strange wave shape) and put together a trial tool with cardboard cut on the laser cutter.


A very rough test tool.



PVA glue is supposed to make mortar stickier, so I tried the tool using regular mortar with added PVA. The clean edge worked, but it wasn't sticky enough- the mortar still fell off when I tried to press it to the other brick. So I tried plaster again, with the tool, but the plaster stuck to the tool as well. And it stuck to the trowel, so even if the tool was made of metal that wouldn't help.


I think what I might have to do is go back to the previous system, but instead of putting the resin right at the bottom of the joint, I will put it closer to the middle. This means I will have to pack in mortar from both sides (from the bottom as well- that will be another challenge) but it means I will have more control over the finish of the joint. And what I can do is build a tool that allows me to apply the adhesive from a tube without wobbling. For the first test I was just using a caulking gun. I needed two hands to operate it and it still was shaky. If I build something like the extruder I was working on last fall, I can perhaps extrude the adhesive with one hand and move the brick with the other.

Sunday, May 12, 2013

Gap Filling 101

Bricks and mortar are a natural pair. Interesting fact: the phrase is an idiom with two meanings. The first meaning is simple or basic: a "The online course covered only the bricks-and-mortar of the subject". The second meaning describes a business that has a physical presence instead of only an online one. "The startup began online, but shifted towards a brick-and-mortar presence in major cities".

Mortar, however, is only one option for joining bricks. Mortar, grout, and caulking are all words that can be taken to mean a plastic substance that fills a gap between two solid objects. As well, there is a spectrum of resins and adhesives that can also be used to bond masonry. Here is a basic overview of some options.

Lime Mortar: This kind of mortar has been used for millennia. Its basic composition is lime putty and sand, although many additives such as plant fibres and clay have been used to improve its strength and flexibility. The Chinese even added sticky rice.

Cement Mortar: At the beginning of the 20th century, Portland cement began to replace some of the lime in mortar mixes. It was favoured due to its quicker setting time and higher strength. It has now entirely replaced lime for most conventional masonry. The basic formula is one part cement to 5 or 6 parts sand. Sometimes hydrated lime is added for increased workability, but this is not the same compound as the lime putty used on its own for lime mortar.

Grout: The Portland Cement Association differentiates between mortar and grout only by their fluidity, with grout being more fluid. A grout mixture is often used in concrete block walls to fill the voids and set rebar.

Epoxy: This substance normally comes in two parts, a resin and a hardener. They must be mixed in order to start the chemical reaction that sets the substance.
A resin adhesive can have different chemical compounds as its basis. Epoxies, polyesters, and vinylesters are three different classes of compounds that perform similarly.

Caulking: The words "caulking" and "sealant" are often used interchangeably. Caulking is often used to waterproof joints and is not structural, unlike mortar. It is often made of silicone.

So, which do I use for the roof? More on that later...