I studied paper conservation so this is technically out of my wheelhouse. But while I was doing my MA we had an external tutor come in and demonstrate how to conserve various synthetic paints. The problem you’re having is the pigment has become friable as the solvent has evaporated. It may be possible to replace some of that lost solvent by exposing the signature to the right solvent in a gas chamber (stuff that you should leave to a professional conservator that works in this medium). The signature will still be susceptible to being abraded off so a cover would be needed. Preferably one that doesn’t contact the signature.
Professional conservation work is not cheap so you’d need to get a quote and judge if it is worth it to you.
It looks like the solvent from the ink has stained the case which will be more permanent than the friable pigment. You could just accept that the pigment is going to fall off and live with the signature’s underlying stain (though you’d still probably be wise to put a clear case on the phone to reduce the abrasion caused by handing and pocket storage). Be aware that the stain may become less recognisable with age (like an old tattoo) as the solvent spreads on the case.
If you are keen to try to fix it yourself the most important thing to do is get your hands on the exact same marker and a similar substrate as the phone body to test any proposed solutions. Give any test time to show itself. I relabeled thousands of books in an archive with a permanent archival pen then put adhesive clear covers over them, after five years none of those labels are readable anymore as the solvent in the adhesive made the ink spread. They were fine while I still worked there but I was getting some stink eye when I paid visit those five years later.
I studied paper conservation so this is technically out of my wheelhouse. But while I was doing my MA we had an external tutor come in and demonstrate how to conserve various synthetic paints. The problem you’re having is the pigment has become friable as the solvent has evaporated. It may be possible to replace some of that lost solvent by exposing the signature to the right solvent in a gas chamber (stuff that you should leave to a professional conservator that works in this medium). The signature will still be susceptible to being abraded off so a cover would be needed. Preferably one that doesn’t contact the signature.
Professional conservation work is not cheap so you’d need to get a quote and judge if it is worth it to you.
It looks like the solvent from the ink has stained the case which will be more permanent than the friable pigment. You could just accept that the pigment is going to fall off and live with the signature’s underlying stain (though you’d still probably be wise to put a clear case on the phone to reduce the abrasion caused by handing and pocket storage). Be aware that the stain may become less recognisable with age (like an old tattoo) as the solvent spreads on the case.
If you are keen to try to fix it yourself the most important thing to do is get your hands on the exact same marker and a similar substrate as the phone body to test any proposed solutions. Give any test time to show itself. I relabeled thousands of books in an archive with a permanent archival pen then put adhesive clear covers over them, after five years none of those labels are readable anymore as the solvent in the adhesive made the ink spread. They were fine while I still worked there but I was getting some stink eye when I paid visit those five years later.