Given that you're considering polyurethane, it's not clear what you mean when you say you want to avoid refinishing. Polyurethane (and anything else that would give you the results you're looking for) is a new coat of finish. Chances are good that you'll need to remove the old finish before applying the new one. In other words, refinish.

Is there anything I can do without completely removing the old finish? Wax, maybe? I was hoping to be able to just clean and cover/seal the finish that's there. I love the character that the table top has and don't want to remove it, just make it easier to live with.

Or am I misunderstanding refinishing? I'm assuming that means stripping down to bare wood, sanding smooth and basically starting over to make it like new. Is there some way for me to just remove whatever is on top without going all the way, so to speak? I don't want to have to restain the tabletop or sand every little nick out.

Am I just being unrealistic?

Get a glass sheet cut to match.

Plastic scratches very easily and looks bad quickly.

You can get a finish amalgamator, that is basically lacquer thinner. This will dissolve the top coats and smear around what's left, that you can then wipe up with clean rags. Hope's and Formby's are two brands that come to mind. There are a number of companies that make these, often known in the trade as ATM (acetone, toluene, methanol) strippers / rejuvenators / restorers. Some have wax in them to slow the evaporation rate, others do not. I'd recommend if you want to go this route to use a non-woven abrasive such as Scotch-Brite or the Norton or Mirka equivalent instead of steel wool. Steel wool can leave behind minute shards of steel that can later rust and cause you problems.

Technically, this is stripping, though in a gentle sort of way. If the existing finish is 90 years old, it has probably lived a long and useful life and is no longer the best choice to just cover over.

As far as which finish to choose, you have a lot of options. You pick the characteristic(s) you want in a finish and you get the concomitant attributes that go along with it.

Polyurethane, in my opinion, tends to get over used. However, I would not be adverse to using it for an everyday dining table with children. For a beginner, a wipe-on version is easier to master than a brush on version. You can either get your own varnish in a can and thin it with equal parts mineral spirits, or buy a pre-thinned version. General Finishes Arm-R-Seal is a medium-bodied wiping poly. I prefer it to Minwax's version that I think it thinned down way too much.

A very similar discussion was posted just a few months ago. You should read the responses to that.

Here is a link that might be useful: Vuja De

"You can get a finish amalgamator, that is basically lacquer thinner. This will dissolve the top coats and smear around what's left, that you can then wipe up with clean rags."

Make sure you test.

Many varnishes are not soluble in anything once they have cured.

Oops, yes, Lacquer thinner will remove shellac and lacquer. These are the two most common production finishes in the last 100 years. Won't do such a good job on varnish or paint.

What would concern me about an amalgamator is the stated fact that there are already other things sitting on the finish; Murphy's detestable oil soap, and an oil-type furniture polish. Either of which could play havoc with trying to get an amalgamator to work reliably. I would first do a strong cleaning to remove everything that's not the finish. With a clean surface, the table could be amalgamated or have a wipe-on thinned varnish applied.
Casey

would clean the table, and then apply a wipe-on varnish.

Here is a link that might be useful: varnish

Thank you all so much. I had tried searching for similar topics but didn't find the one mentioned. Thanks for linking to it!

I know it needs a thorough cleaning before I do anything, as mentioned by Casey and sloyd. What should I use for that? I've seen some sites where just mild soap and water are recommended, and others who recommend stronger cleaners and/or solvents such as mineral spirits.

Again, thanks for your patience and help. :)

Nice table. First thing first. What finish is on there now? In general, any finish that was used prior to WWII would be shellac. Get a small can of alcohol and wet a rag with it and rub a small spot to see if it takes off the finish.
Any job to rejuvinate or refinish a table takes work and time.

>What should I use for that? I've seen some sites where just mild soap and water are recommended, and others who recommend stronger cleaners and/or solvents such as mineral spirits.

You really need both, because each takes off different types of contaminants. Without getting too much into chemistry, there are things that clean up with water (a polar solvent) and things that clean up with (non-polar) solvents such as mineral spirits.

If your finish on there now is that degraded, I'd be leery of just adding more over the top. Stripping of some type is needed.

Of course, none of us can see or test the finish, so our approaches may be varying and subject to change as we do "research" (a euphemism for "trial and error").

I have a leaf that's pretty badly warped and split that I can use for testing, so I can "research" without messing with the whole table. A small can of alcohol--what kind? Denatured? Should I use soap and water first to get the surface dirt off?

Here is a good link to a document, on furniture revitalization.

http://extension.usu.edu/files/publications/publication/fl-hi-500.pdf

Furniture Cleaner:
http://www.rockler.com/product.cfm?page=6354

"Should I use soap and water first to get the surface dirt off?"

Or paint thinner, really about the least harmful of the cleaning solutions you can use.

Water is a problem if there are any defects in the finish.

I read through all the links you all so helpfully gave me, plus some others. I decided to use mineral spirits to clean it, then spot-test with denatured alcohol. If the finish was shellac, I'd try playing around with the alcohol and some new shellac to see what I could do--reamalgamate, overcoat, or what.

I experimented today. The finish is definitely shellac-- denatured alcohol easily melted it. So I took my warped and cracked leaf and cleaned it well with mineral spirits, then used the alcohol and wiped off all the old finish I could. Then I put on a thin coat of shellac--I didn't do a great job, but I knew I was just experimenting. I really just wanted to get an idea of what a finished product might look like. I'm really pleased with how it looks!

The one thing I'm still not sure of, though, is whether a shellac finish is what I want. It looks beautiful. But is it durable? My whole point is to make the table water-resistant so I can easily wipe up spills and that sort of thing. I've read conflicting information about the durability and "wipeability" of shellac. Is it really an okay choice for an everyday kitchen/dining table (with kids)?

Then, No, it is not the finish to use on anything that gets used like that. But, it is fine to use under most finishes as a sealer coat, especially if there is any smoothing or fine sanding to do to prep it for a top coat. I do a lot of finishing, so I have preferences, but they only seldom involve polyurethane. So, I may not be the person to recommend a finish.

Just a note though: A professional finish, given most applications, would be a sprayed pre-cat lacquer. It isn't the best thing in wet environments, however, and so varnishes most often are used for rough and/or wet environments. Polyurethane is a varnish, it just uses synthetic polymer resins at its core. Varnish is just a resin combined with an oil, usually linseed oil. My personal preferences are for old-school varnishes, or what most refer to as "oil-based" varnishes. There are many out there although, not all good. Someone else will have to tell you the best brands of polyurethane varnish to look for.

I do like General Finishes Wipe-on poly, but I think a wipe-on will be too thin for a table top application.

If you decide to use varnish, the best for harsh or wet environments are marine varnishes. There are several good ones.
Richard

One other thing...
stop using furniture polish and Murphy's.

Shellac is what is making white rings and softening in the heat. New shellac will not be any more durable than the old.

Remove the dirt, use alcohol and steel wool to get rid of the shellac, then use a modern finish meant for table tops. My preference is a gel polyurethane because it's easy to do.

shoe polish - really pick a color close, not too dark and use the way you would polish shoes.

Unfortunately, shoe polish is basically a pigment stain and a little dye in a solvent (naphtha or turpentine)and emulsified wax, and as we all learned in wood shop, pigments just sit on top of the wood, while dyes soak in. Pigment stains are used all of the time, but rely on an in tact top coat to stay fast. Wax, unfortunately, makes it difficult for top coats to adhere. Ergo...

I think this was suggested before, but, get a piece of glass cut the size of the table top until your kids are old enough to know better. (Or, if you're like me, and your husband still isn't old enough to know better, just leave it on all the time, save for holidays/dinner parties)

And then don't ever buy Murphy's Oil Soap or Old English ever again.

"And then don't ever buy Murphy's Oil Soap or Old English ever again."

Pledge is even worse.

It contains silicone and makes it a PITA to refinish.

So I'm back where I started, with poly. That's what I'm going to do. But first I'll remove the old shellac with denatured alcohol then apply a thin coat of new shellac. A light sanding, then a few coats of poly. I'm guessing some of you will recommend against this. I've read in some places that poly won't adhere well to shellac, but I've read in enough other places that it works just fine. I love the look of the shellac so I'm willing to risk it. I just don't think I'll get that same look with poly alone.

The problem with the glass idea is that I change the size of the table somewhat frequently. I have 12 leaves, so it can go from a small table for four to enough room to seat 14 adults comfortably. I really like being able to just pop in a couple of extra leaves if friends or family come for a meal, or take them all out if we need floor space.

I can't thank you all enough for your help and advice. I've learned so much in this whole process! I'll post pictures when it's done. :)

>I've read in some places that poly won't adhere well to shellac, but I've read in enough other places that it works just fine.

Just be sure to use dewaxed shellac. Zinsser's SealCoat is a good choice. Poly does not adhere well to waxed shellac.

General Finish's Arm-R-Seal would be a good choice for a poly. It's a wipe on finish, so needs more coats, but they go quickly and easily.

Have you tried Howard's Restore-A-Finish? Great way to freshen up old wood without having to strip the finish off. I'd try that, than coat tung oil or finishing oil on top.

Yes, I've tried "Restor-A-Finish." Not impressed.

Funny to see this pop up in my email after 4 years! My table project turned out beautifully. I used denatured alcohol to remove the old shellac, then I applied two coats of thinned shellac followed by 6-9 coats of wipe-on satin finish poly (I lost count). I did no sanding at any point in the process. The table kept its old character while getting a good clean-up and durable finish. My sister is now in possession of the table as I'm living out of the country, but she uses it every day and from the pictures I occasionally see it's holding up great.