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    Home made FSM for AH or idx-mirror
    From: Igor S.
    Date: 2019 Sep 28, 12:47 -0700

    FSM mirrors are expensive and being cut to circular shape even more expensive x4-times (see for example https://firstsurfacemirror.com/glass-first-surface-mirror/  ). My rectangular FSM 6mm plate I bought from ebay for 20$.

    Recently I came up with an idea of converting normal mirror in to FSM for further usage in artificial horizon. The idea is not new ( https://www.youtube.com/watch?v=IaEaaeajCSI ) and is pretty clear - somehow to remove the protective layer on the backside of the mirror.
    When I was building my kayak (my other hobby) I varnished it in the end with a 2-component polyurethane varnish and I also had a solvent for it. This solvent is aimed to dilute the mixture or to clean the brushes after working with polyurethane varnishes (or epoxy). I tried this solvent and it worked like a charm for this specific task! In this way I have managed to convert normal mirrors in to FSM mirrors. All the work has to be done in open air and with protecting gloves for safety reason.
    The recipe is the following. Put the mirror with wetted backside in to a plastic bag and leave it for 24h until the protective layer became softy. Then scramble it with a plastic card applying the same solvent to keep it wet and clean the surface.
    First I have managed to convert IKEA -mirror into FSM. IKEA sells very cheap 2mm thick mirror panels. Some very cheap mirrors (usually 2mm) does not require waiting for 24h. Apply the same solvent to the protective layer and gently wipe it out with a soft tissue (see photos below).
    I am living very close to a glass distribution company where they cutting glass and mirrors regularly and have a recycle container full of broken pieces of different shapes and thicknesses for free. There I could find many pieces of 4mm - 6mm mirrors which can be cut into rectangular and then in to circular shapes.
    Speaking about the quality of obtained in such a way FSM I must admit that some minor scratches are possible and moreover the mirror became semitransparent in contrast to manufactured FSM of optical grade.  These drawbacks have no influence on practical application for artificial horizon and quality of final results (taken sights).
    In this way one can also convert if he wish the index mirror of a sextant to FSM.
    (see my older post http://fer3.com/arc/m2.aspx/Index-mirror-type-IgorS.-mar-2019-g44608 )
    I attached several photos of converting to FSM a very cheap 2mm-make-up mirror and 6mm mirror plate (from the aforementioned recycle container).
    Last but not least the whole process is fun!
    kind regards,
    Igor
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