recommend varnish type for transparant acrylic

[ufotds]

I want to protect the paint on acrylic compass baseplates like these:

http://www.trekkinn.com/outdoor-wandelen/suunto-a-30-cm-l-nh-compass/6902/p

The paint wears of to fast and you have to replace them because you cannot read anything on them anymore.

I need the varnish to be hard (scratch resistant) completely transparent and should not yellow, should be completely weather proof.

I have tried so far with an MSA varnish from goldenpaint, but it was to soft and gets ugly even by scratching with a fingernail.

any recommendations for this?

thanks in advance

 

[MikeHalloran]

Put the paint on the back side and let the acrylic protect it.


Mike Halloran
Pembroke Pines, FL, USA

 

[ufotds]

Hi,

actually I want to protect existing baseplates which have the paint on the back as the most outside layer. So I want to put an extra layer over the back to protect the paint from scratching of.

 

[MikeHalloran]

Would another layer of acrylic, say .01" to .02" thick, cause you problems with parallax? Solvent bond it, laminating the paint.



Mike Halloran
Pembroke Pines, FL, USA

 

[ufotds]

parallax would not be a problem, do you know of a specific product you could recommend? This is not for industrial purposes, so it should be feasible for a small batch like say max 30-50 pieces without the need for expensive equipment.

note that the bevel in the middle needs to turn, so preferably it should be applicable locally, as in a liquid form or spray.

thanks for your help

 

[Demon3]

Why not buy some iPhone screen protectors, trim to fit and apply? Could be a nice solution.

Failing that I'd buy some clear varnish spray cans and try them.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[MikeHalloran]

I'm thinking buy a sheet of acrylic, cut some rectangles out of it, punch holes to clear the rotating part in the center, and solvent bond.

To make it really nice, you will probably have to mill the shape, not shear/punch it, and anneal the acrylic after cutting.



Mike Halloran
Pembroke Pines, FL, USA

 

[ufotds]

How would you go about applying the solvent to the entire surface? Can it be sprayed or brushed? Would this whole process not become much more complicated that to apply some sort of hard varnish?

 

[patprimmer]

Are you an engineer.

Are you even a tradesman or handyman.

Of course fabricating a part from sheet then attaching it is more complicated than spraying a coating onto it, but ir also gives a thick solid protective layer.

The existing coatings may interfere with the process or may be damaged during further coating.

Engraving the surface of the acrylic before the original painting will protect the pain, that is if you engrave in only the areas to be painted then only paint in those recessed areas.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[MikeHalloran]

Or just buy them from a different source.
The one I got as a Boy Scout has the markings hot-stamped on the back face of the baseplate, then filled with paint.
Granted, it hasn't seen much use in recent decades, but the markings still look fine.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

OR, if you _really_ want to differentiate them, get backplates machined from polycarbonate, so they won't break, and get the markings laser-engraved in the middle of the thickness, so they can't be rubbed off. Lasers can do that. Unfortunately, you can't paint markings made that way, because you can't get the paint into the isolated cavities.



Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

Along Mike's first suggestion, a strip of packing tape, the clear kind.