Brass restoration help please

[Pete2112]

I'm restoring an old brass plaque which is about 200mm by 130mm and has engraved lettering on it. I removed all the dirt, tarnish, and the bits of old black paint remaining in the letters, polished it to a shine and filled the engraved lettering with black acrylic paint, and it looked superb.
I then used a new spray can of clear lacquer specially formulated to prevent tarnishing on brass and other shiny metals. The lacquer coat bubbled slightly and went a little foggy in places. So I cleaned off all the lacquer using methylated spirits and acetone, but in doing so made a mess of the black painted lettering. Carefully removing the remainder of the black lettering without scratching the shiny surface was a time consuming job. I've now eventually got back to the stage with the black lettering back in the engraving. After all the extra work involved in getting it back to looking perfect and new, I'm having second thoughts about using the lacquer again and chancing more problems. This bit of restoration is a surprise Christmas present for a family member. With the big day fast approaching, I am looking for advice as to what might have caused the lacquer problem and how to avoid it. Or maybe I should just chicken out, quit while I'm ahead, and wrap the thing up ready for Christmas, in which case it will tarnish again much sooner than I'd like.
Any input would be helpful.

 

[JohnD]

Did you warm it first?

How did you clean off all traces of polish?

 

[Pete2112]

I didn't warm it but it was all done indoors at about 19 or 20c and both the lacquer and plaque had been at that temperature for a day or two prior.
After polishing I thoroughly cleaned it with methylated spirits including using a toothbrush to clean inside the engraving. I then washed it in hot water with fairy liquid, and dried it with paper kitchen towels. I flooded the engraving with watered down acrylic paint. Squeegeed it off which left a bit of thin paint smearing on the shiny surface. When the paint had dried for about 3 hours, I carefully cleaned the dry smeared paint using paper towels and cotton buds around the lettering, all dry and no chemicals or liquids. Then, when it was looking perfect, I shook the can for a minute (Tableau Anti-Tarnish Lacquer) and sprayed carefully and fairly lightly in several quick passes. 15 minutes afterwards I noticed some small areas of grey and a few tiny bubbles. Then I decided to remove it and it was still tacky in places.

​

 

[Pete2112]

This is the plaque in it it's tarnished state and how it looks now (no lacquer). I didn't think to take a pic of the lacquer problem, as at the time I was only concerned with removing it.

 

[Old Salt]

Get a piece of brass and paint some letters on it and try different methods to see which “flavour” works best. Personally I would try clear varnish (brushed on) rather than lacquer although petrol resistant clear lacquer may also be worth a try.

 

[JohnD]

Yes, I've only used the brush on type, and it runs smooth better if you warm the brass first. I can't think of the brand name. Might have been Rustin's. Might be a copal varnish.