I like tin ceilings painted. After all, they were originally conceived as a substitute for decorative plaster ceilings. I once installed a 1600 sq ft tin ceiling/cornice in a victorian storefront. The tin came painted with silver primer to prevent rust during installation. I would fear that the stripping has left your ceiling vulnerable to rust. They are actually stamped steel sheets, not tin.
If you don't mind me asking, how did certain areas get the blued color?
Casey

Most base metals ( I think base metals are the common
metals used for industrial use) have a simple chemical
treatment to cause them to

a. get shiny
b. add dark tones
c. go black

Tin is metal used for battery contacts in cell phones.
It's not easily oxidized and this is why it's used.

This is why I'll state now that I don't think the color
will change and won't require a sealant. however I doubt that your color is the tin chemically changed. And so if
the color is just the inks in the paint they might change.
I doubt it. Only UV light and ozone and stong oxidizers (chemicals) can change or fade ink colors.

IF you want to test a spot for ink use acetone to try to
see if your white / acetone cloth will pick up the color
when you wipe it. A water soaked cloth will pick up
color if the ink is losely bonded to the tin. It's more
likely to change if that's the case but I would not seal
it. Sealing tin is like sealing a gold ring. Why do it
would be my first thought. The tin is beautiful and
valuable.

Tin remains shiny in nearly any environment as far as I
know. The covering you had on the ceiling probably
left it's own color behing but probably did not chemicaly
change the tin. So if you want it shiny you might only
need to clean off the color from the covering.

Wikipedia should have an excellant reference about
tin, the metal.

I don't believe it's magnetic. If you use a new style
rare earth magnet it should find any small amount of
non-tin magnetic metals in the ceiling. ie: nickel is
magnetic. iron is magnetic.

Any product you find will have an MSDS for it. Look that
up and read what's in the commercial product. Then
if you choose you can buy the chemical (s) that are
in the product , save money, become a bit of an expert,
and often get better results than with a product.

Look up keywords in Google like

"tin brightening"

Using quotes will make sure you land right on top of
the kind of pages you want.

adding another word like the name of the chemical(s)
you found in MSDS will also put you right on top of
pages that cater to companies involved in doing the
process you seek.

Good luck

Andre

I've used Penetrol with great success on bare iron and steel that I didn't want to paint, although I don't know how/if it works with tin. Might want to check out if a simple rub of Penetrol (once you have the color you want, shiny or dull) might do the trick?

Thanks everyone.

Casey, I don't know about how the blued color happened. I know that there was no primer at all between the metal and the many, many layers of paint that were chipped off. There was a navy blue paint among the layers but it wasn't the first layer. I was assuming the blued color was some sort of natural darkening, enhanced or hurried along by the chemicals in the paint.

Gardurnit and Circuspeanut, thanks for the info. I can do a quick acetone check and then also look into Penetrol. My husband might be more open to leaving it unpainted if he could lighten some of the darker parts, but I don't want a shiny-happy ceiling.

If in doubt as to what kind of metal it is, a magnet will stick to ferrous metals (iron and steel), but not to any other metals.
It is generically called "tin ceiling" but it is steel. Much in the same way that a "tin can" is also steel.
Casey

The blue to yellow to tin color change is from heat. It happens alot when metals are stamped out of big machines with dies (like ceiling tiles or old tin pots and pans) and not wire brushed or rubbed off. Alot of "tin" items still have this metal color change but it is usually under some paint or enamel. If you like the color you could make the whole piece blue with a little blow torch going around in circles on the ceiling and stopping when the heat meets the color you want.

The following link shows a guy doing that but with copper and it kind of shows what I am talking about. If you wanted to attempt this I would defiantly say practice on some scrap pieces before you went to town on the ceiling.

Here is a link that might be useful: Copper flame work

Please don't paint this. It is SO beautiful with this patina.

My sister had a tin ceiling installed in her kitchen a few years ago. To keep it as original, the company suggested she gave it a coat of clear lacquer. It worked; after more than 2 years, it is exactly as when it was first installed. Maybe you could consider this to stop any new "darkening".