Most of the comparative shots showing the results of various actions are grouped towards the end of this post to make it easier to assess the effects of each stage in the cleaning process. In the meantime, here's the story as it unfolded.
The dirty beast was carefully wheeled to the wash bay...
At some stage there was a glycol spill in the payload & a few drops made it onto M5. These spots were really bad so we didn't particularly rate our chances of removing them. The images below show that part of the mirror in the normal fluorescent light of the clean room (left) & illuminated with a LED flash-light (right).
Clean, dry compressed air was blown over a quadrant of the mirror to see what effect that would have on all the loose particles on the surface. The effect was noticeable, but not nearly enough.
Next, that quadrant was rinsed with de-ionised water for a few minutes.
& that was followed by a distilled water rinse for another few minutes.
Drops that remained on the surface were then herded either down the central hole, or over the outer edge with the clean, dry compressed air.
The result of the rinsing was encouraging - the images below compare the dirty side with the rinsed quadrant (top & bottom frames respectively).
However, closer inspection with the brutal LED flash-light showed that although the rinsing had removed a lot of the dirt, the process had also produced awful streaks...
Further rinsing efforts made no significant improvement so it was time to haul out the horse soap (see yesterday's post for more about sodium lauryl sulphate). Since the outermost 20 mm of the mirror isn't used, we opted to try the soapy cotton wool on a section of the edge first. The soap was left to run down the rest of the mirror in that sector & rinsed, as before, down the central hole.
The effect was dramatic & so the rest of the edge was given the cotton wool treatment. The whole mirror was kept wet with the soapy solution while the edge was being cleaned, then the usual rinsing & drying processes followed.
It was a team effort with Jonathan keeping the mirror wet, Francois providing the soaked wads of cotton wool & Hitesh dragging the cotton wool.
Not to mention the Irish barman in the back, shaking up his legendary sodium lauryl sulphate cocktails...
The edge had clearly benefited greatly from the cotton wool cleaning so the next step was to do the same for the rest of the mirror. Larger pieces of cotton wool were used for this, dragged uphill, 2 passes per strip.
Yet more rinsing (& drying) after all that...
& finally - a beautifully clean M5 :) Note that the white spot in the image below's Not glycol related, it's actually light from the LED flash-light bouncing off M5 & onto the plastic sheeting that covers the roof & walls of the wash bay!
One of the major highlights of the day was emerging from the clean room for a much needed break & finding that a batch of Hannah's outrageously wicked chocolate brownies had been delivered to the SALT kitchen! Thank You Thank You Thank You :) :) :)
The next image shows the results of the main steps in the cleaning process, from left to right & top to bottom:
- The filthy start.
- Dust blown off the top right quadrant with clean compressed air.
- Right half rinsed with de-ionised & distilled water, dried with clean compressed air.
- Cotton wool soaked in sodium lauryl sulphate dragged along a sector of the outer edge & the soap allowed to run down in that sector, then rinsed & dried as before.
- Whole outer edge treated as in the previous step.
- As above, but the entire mirror cleaned with cotton wool soaked in sodium lauryl sulphate.
Before & after (left & right), illuminated with a LED flash-light & the camera flash (top & bottom). Spots on the dirty mirror are from Glycol while those on the clean mirror are reflections off the plastic sheets that line the wash bay.
More than 500 photos were taken in here today... A thoroughly amazing day & a superb job by all involved!