Take it to a good dry cleaner

cold water and woolite.

I'm thinking: cold water, very gentle soap/detergent, soak but do not twist, scrunch, etc. Rinse thoroughly, then roll gently in a shamwow to absorb as much water as possible (may take a few rounds), then lay flat to dry.

Some advice here:

http://www.sewgirls.com/needlework/30-year-old-crewel-help-to-clean-3508-.htm

I watched this a while ago and liked it. Might be helpful.

I would contact the textiles department in a local art museum for recommendations. In my experience, conservators are always happy to help.

Ditto on contacting the conservators at your art museum textile department. Congrats to you all on kicking the habit, and boy how I do adore crewel.

Agree, contact a museum, perhaps the National Textile Museum in Washington,DC is a good place to start. They would know of regional museums with local textile experts.
www.textilemuseum.org

good luck.

If it is cotton thread, it could bleed.You could identify easily because cotton is shiny and wool is dull. If she used a commercial kit, only one kind of thread would be provided. If you use water to wash you could have puckering around the embroidery, Never iron the top of the embroidery because it would squash it, cushion with fluffy towels, and iron the back only, with low setting. Maybe you could vacuum it, reframe it, and accept the yellowing as part of being an antique, The Martha Stewart link refers to washing linen without embroidery. The stain might be permanent, and you would risk ruining, and not getting rid of the stains.

Don't use woolite. Soak in cool water and baby detergent briefly and blot to dry. It may take sever tries and chances are not all the yellowing will be removed, but the dust and surface dirt should come off.

My parents were both heavy smokers. The paintings and textiles I took from their home were all very yellow and coated with a sticky deposit that was almost impossible to remove. I'm not sure a dry cleaners is a good bet unless you have one that specializes in handwoven rugs and textiles.
Find a book on needlepoint or crewel that explains cleaning and blocking. I have successfully washed old needlepoint and embroidery by hand in cold water and then blocked it by tacking it to a board. Good luck.

I'd have it professionally cleaned. Take it off the stretcher first, and have it re-stretched when you have it framed. You can very easily destroy embroidery by mishandling it.

You can find a textile conservator in your area by going to www.conservation-us.org.

Please contact a museum??? what has happened to this country?!!! :-) Take it out of the frame, wash it in warm water with woolite or any old soap. Let it sit for a while and everything will go away. The yellowing will not, no matter what you do.

The first think to worry about is the fact that the textile was mounted on wood stretcher strips. Do NOT was or clean it. The acid in the wood probably made the embroidery brittle in those areas. You know those brown stains you see on linens - they are from wood. You won't see the damage until you have cleaned it (same as moth damage) and the piece could disintegrate. There is a lot about this on-line.

This is a general article - in mentions wood and testing materials to see if they will bleed. http://ritchie.ext.wvu.edu/r/download/23470

The Textile Museum has a lot about conservation on its Web site, and there is a lot of info around on textile conservation. That being said, I don't know how much there is on removing nicotine stains - and, just because some this is published...

In any case here's some articleshttp://laundry.about.com/od/stainremoval/f/nicotinestains.htm. http://www.howtocleanstuff.net/how-to-remove-smoke-and-nicotine-stains-from-wallpaper/

There is no point in taking this to a conservator - it would cost hundreds of dollars and there is nothing they can do about some of the damage. I would have it remounted and reframed by someone who does archival framing and focus on the piece, not the nicotine. You'd be beside yourself it if fixing it destroyed or damaged it.

You may try medical grade benzine (I don't know if it is a proper term in US, it is used in medical facilities to clean the skin prior interventions).
Here it is often used in home settings to dissolve any oily/waxy stain or residue - we use it frequently to remove the band aids without tears (and leftover stickyness) :-)
Benzine will dissolve nicotine/tar stains, but I'm not sure what it will do to the embroidery floss.
Just my 5 cents...

It's not worth the risk of ruining such a beautiful piece by trying to save a few dollars. Have it professionally cleaned.

You could also take it, if resource is available, to the Textile Engineering Department of a university. Georgia Tech did a great job for me with delicate, antique fabric about 30 years ago.

Eucalan! Buy a bottle, soak in diluted Eucalan overnight, and allow to dry flat on a bath towel. Eucalan is specifically designed so that it doesn't need agitation or rinsing out.