My mother saved the christening gown used for all four of her children, earliest being 1948, last christening 1953. The yellowing was very heavy and dark on the bonnet, slip, gown and a coat that had a very fragile, transparent outer layer of ...material with a complex design pattern of small flowers and stems. I was able to get most of the yellow out of the bonnet, the slip and gown by soaking in Oxy Clean. However, it was impossible to get the yellowing out of the coat, the fragile outer layer shredded.
I found Heritage Garment Preservation online. All I can say is thank goodness they exist. They certainly came to my rescue. I explained the situation and the damage I had done and asked if they could help. After receiving the gown they said they could get most or all of the remaining yellow out of all 4 items (they got it all out), and their seamstress could replace the coat's sheer outer layer with a similar or identical material. She would also replicate the small flowers and stems on the outer sheath, and repair a few areas where the lace had separated on the gown.
To say I was very impressed with the seamstress' skills is an understatement -- the entire outfit was beautiful, placed in a preservation box with instructions for future care. You could not tell the outer layer had been replaced. The flower and stem design were perfect. Only those very familiar with the original outer sheath would be able to tell, and only with a very close examination, that the flowers were so very slightly larger, and that a cotton rather than a contrasting silk thread had been used for the stems. Heritage cleaning, repair and preservation of all items was outstanding.
The price was outstanding as well for the amount of work and attention to intricate details made in this repair. I will most definitely keep Heritage in mind if I ever need gown restoration, preservation, and especially if I ever need detailed and intricate sewing in the future. Amazing job, I very highly recommend.