Re: ATM broken cementtool

[Dominic-Luc Webb molmed <Dominic.Luc-Webb@molmed.ki.se>]

On Mon, 11 Jun 2001, Klaas Honders wrote:

>
> Hi all,
>
>          A few weeks ago I made a cementtool for a 13" project.
> This was the first time I made one and it looked excellent till today.
> When inspecting this disk I noticed a very small crack running from the edge
> to the center over about 3".
> Light knocking caused an increase it went on to about 4".


Don't cry.... we're here and will help... :)

What stage of grinding are you at? I am having luck with
concrete and have made new concrete tools only out of
dis-satisfaction in the quality of the previous concrete
tool (could just as well have broken it).

My method may be important if you do not want to spend too
much time on courser grits. First, I lay rice paper over
the mirror. Then I apply tape to make the channel. I add
more water to the concrete than instructions call for. This
seems to be helpful because the concrete pours very evenly
and makes a very smooth negative image of the mirror surface.
I do not use tile, but I guess you might do better than me
if you use tiles (I get more scratching than I would like).
I take a peak at the drying progress within about 10 hours
after pouring. If the surface looks reasonably secure, I
remove the toold from the mirror by removing the tape and
the tool just drops/peels off from the rice paper. I clean
the mirror and wet the tool if it is too dry. I then
start gently grinding with a copious amount of finer grit,
soap and water so as to drammatically reduce any direct
contact between the two surfaces. In doing so, I manage
to get the tool to match the mirror surface very well. You
need to be careful with the edges of the tool because they
tend to be easy to break off. The extra water seems to help,
as does aggitation right after pouring to help get bubbles
out.



Cheers,



Dominic

North 59 37' 30"
East  17 48' 10"