Lens-cleaning room · Velstraven

A small room of chapter 3. When you walk in, the room card reads: Chalk clouds the observing lens; the reference instrument cannot be seen.

Narrated walkthrough

Chapter 3, third upper floor. Through the east doorway of the stalled orrery. Its north door leads to the optional shy specimen.

"Chalk clouds the observing lens; the reference instrument cannot be seen." The glass beneath is sound. Only its edge can be reached by hand.

Lens: The clouded observing lens. Soluble chalk washes off into the wash trough below it.
Drain: Empties the wash trough into the lower wash line.
Observation: The eyepiece in front of the lens. It works once enough chalk is gone.
Reading lamp: Optional light to read the room by: Handle toggles it, Heat lights it, Supply liquid douses it, Place light roots a lasting flame blossom in its cup. It works none of the room's fittings.
Reading shutter: Optional: Handle or Orient opens a high window for daylight from a second angle. It works none of the room's fittings.

A nudge

Cleanse runs a litre of warm wash over the glass. The chalk is soluble, so most of it rinses down into the trough, enough to see through.

The full solution

Aim at the Lens and cast Cleanse surface (Fire, Water, Water).
Cleanse runs a litre of warm wash over the glass. The chalk is soluble, so most of it rinses down into the trough, enough to see through.
What you see: "Soluble chalk washes off the glass into the trough." The lens now reads "Enough chalk has left the face to see through the aperture."
Stand at the eyepiece on the working side and Handle the Observation, or just look through the lens at the ring behind it.
With the chalk thinned, the reference ring behind the glass is visible. Looking straight through the cleared glass records it on its own.
What you see: "The cleared aperture gives a view of the reference instrument." then "Lens-cleaning room settled."

Supply liquid (Water, Water, Water) on the Lens twice. Each stream is half a litre and washes off about half as much chalk as Cleanse.
By hand, no spells: Handle the Lens three times. Each wipe clears a little of the reachable edge ("A reachable edge wipes clear; the recessed face remains coated.") until it reads "The reachable glass is already clear." That is just enough. Then Handle the Observation.

Runoff collects in the trough, which holds 6 L. If it is ever full, washing stops with "The wash trough is full; runoff has nowhere to collect." Handle the Drain to empty it.
Heat only dries the chalk harder, and Obscuring veil or Place light change nothing on the glass.

Nothing can go wrong here; keep washing until the eyepiece shows the instrument.
Hold R for one second ("Keep holding to restart from the room's autosave"), or use the pause door "Restart from autosave", to put the room back as it was when you walked in: "Automatic room-entry save restored." Rooms you settled earlier stay settled.