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Thread: Repainting old lens

  1. #11

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    Re: Repainting old lens

    I had to write a report this week at work about a new line of studio microphones we produce that a painted finish is being considered for... I copied parts of it for suggestions to prevent unwanted outcomes...

    Here are some highlights;


    -Material MUST be exactly, properly prepped before finishing (proper cleaning/de-contaminating/roughing up etc)...

    -Finish chosen for application must be durable, scratch/abrasion resistant, sets well in a reasonable time, applies evenly, and is resistant to chipping/gouging (during assembly & end user use)...

    -High performance coatings (like powder coating) usually require heat baking curing (powder coat processes vary, but 400deg F /10 min is common for other applications)...

    -Finishes tend to be thin, brittle, and taut on surfaces... Material that is thin or somewhat flexible can strain it's hold between it's finish layer... Areas like corners, edges, raised areas etc are under more finish tension, thinner, and tend to make contact with external objects more that cause them to wear more rapidly...

    -Assembly issues include when tensions are applied to finished parts (such as screwing down parts, areas around screw holes, clamping parts etc can cause chipping, cracking, and other
    issues)...

    -Parts are exposed to high heat during curing processes... This can effect parts fit tolerances (heating causes metal to expand and upon uneven cooling , there can be local deformation that can
    allow thin materials to to buckle, wave/distort, and create tensions that can reject finish coat...

    -Pre-finished surfaces not properly decontaminated can leave residues that can affect finish adhesion, or if they out-gas during curing, they can blister, chip etc...

    -Some production processes containing solder (such as attaching frames to mesh screens) are close to melting temperatures used in the curing step, and can melt the solder if oven temp gets slightly higher than normal... Uneven heating/cooling can cause uneven finish surfaces or unequal tensions in finish or parts...

    -Some finishes hold handling fingerprints, body oils/acids well, and can penetrate finish or part surfaces...

    -Powder finishes are porous, and if over steel etc, can allow excessive moisture/humidity or environmental issues to penetrate, and possibly cause internal corrosion eventually, affecting finish &
    material...

    -Finishes "soften" the visual lines of a product's appearance, and light reflecting from a finished surface can change it's color/hue, possibly causing a different effect than the base color...



    Recommendations:

    -Look at pros/cons of different finishes...

    -Thorough review with vendors, research regarding the type and application of a finish, and the effect (finish & process) on parts...

    -Pre-checking test samples for resistance to chipping, damage, during test assemblies, and short/long performance tests to see how they survive different assembly processes and field use...



    Just a head's up that might keep life happier/easier for us all!!! :-)


    Not too different for foto gear, just other considerations to consider!!!

    Steve K

  2. #12
    Jac@stafford.net's Avatar
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    Re: Repainting old lens

    LabRat, I have a great experience with powder paint. For my old Harley-Davidson chop I used powder painted drag bars, front forks and several other parts which have not faded, chipped or worn for about thirty years. Reading your article it seems my experience is unlikely, but is true. Very Best, Jac.

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  3. #13

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    Re: Repainting old lens

    Quote Originally Posted by Jac@stafford.net View Post
    LabRat, I have a great experience with powder paint. For my old Harley-Davidson chop I used powder painted drag bars, front forks and several other parts which have not faded, chipped or worn for about thirty years. Reading your article it seems unlikely. Very Best, Jac.

    Click image for larger version. 

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    True, but with some small, thin, precise items, there are considerations at play... On big, broad surfaces, it's great, but small complex, thinner surfaces are another matter...

    I spent time re-finishing damaged camera tops, lens barrels etc, and there are short/long term hairpullers that come up...

    I second direct metal treatments already suggested...

    Good luck!!!

    Steve K

    ps/ I wanted to add that what our firm's concerns were about how heat curing process would possibly affect thin materials such as sheet metals, wire mesh, etc... This was what the report was about... Heavier stuff like lens barrels should be OK if even heating/cooling was applied, but there is still the possibility of things like tight threaded stuff to slightly distort... And the likelihood of the finish to be too thick, as too affect operation of rings, etc... sk

  4. #14
    Jac@stafford.net's Avatar
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    Re: Repainting old lens

    Quote Originally Posted by LabRat View Post
    True, but with some small, thin, precise items, there are considerations at play... On big, broad surfaces, it's great, but small complex, thinner surfaces are another matter...
    An excellent point worth repeating, thus the reply with quote. Thanks for that.
    .

  5. #15

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    Re: Repainting old lens

    If its aluminium then you will probably first need to use an 'etch primer' designed for aluminium, then use a compatible top paint. You should be able to find out more by searching the web. Aluminium can be problematic to get other types of paint to stick to.

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