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Turpentine is flammable. It is dangerous to pour it over an open flame. The consequences of this mistake could be disastrous.

In spite of our best efforts, when pouring the pitch lap, the pitch may insist on flowing over the edge of the tool. Let it go and press the lap anyway. The overflow may be cut away and cleaned up afterwards.

If the mirror face is not sufficiently wet when it is first laid on the warm pitch it may drag off the entire upper layer of pitch with it when it is removed from the tool (this may also occur if the pitch is too hot when poured). Don't panic, just tear the pitch off the mirror face with wet fingers, re-wet the mirror, pour some more warm pitch on the tool and then try again. Move fast, but don't panic, if worse comes to worse, scrape off all the pitch from both surfaces and start over.

Pouring a pitch lap in this way is a hasty procedure. Don't try to read the instructions as you go. It takes much longer to read about it than it does to do it.