Photographing to reveal illegible signatures


Well-known member
I recently had the good fortune of picking up a completely hand made, hand tooled mahogany drop leaf dining table with 4 leaves. All are single boards including 21" drop leaves and hand made extension runners. The hand plane marks are quite evident such as scrub plane marks on the underside and fine tell tale cabinet scraper scratches on the surface under a very fine shellac surface. I have been in the business for nearly 40 years and this is a very well crafted piece. I have disassembled the apron and runners so I could add hide glue to the loose mortise and tennon joints and found some barely legible signitures on the underside of the main top. I tried to photograph them with various settings on my 35mm digital and that has made it clearer but not good enough. I've read somewhere that the museums have a method that they use to enhance the signatures and I'm not sure what it was or where I read it. I'm thinking black light and perhaps the American Furniture series. The signatures are either a blue chalk or crayon. Any advise?
Have you used Photoshop (or a similar image editor) to try to get the signature to stand out more?  Photoshop can do some unbelievable things with images. Could you post a copy of the image?

Photoshop sounds like a good first-try choice, 'tho I am technically-challenged with respect to computer software.

If that doesn't work, I do know that use of a 35mm film camera loaded with various black-and-white films and colored filters will probably work.  If this sounds like a project, it probably will be, but it could be worth it.  Two thoughts: also try infared film, and with B+W films remember that a blue filter will lighten a blue subject while a reddish filter tends to darken it.

In an article of APF vol 7, I mentioned how a black light was used to help make an inscription a little more legible. Preston is right though--take your image into Photoshop and you can adjust the contrast in different channels to pick out details.

Be open to the possibility that you may have your best success by processing the inage in pieces; that is, the photoshop affects will vary over the image area, and one average set of settings may not yield you as much information as a series of shots with slightly different settings suited to the conditions at that portion of the image and then pieced together.

I often use this approach with success in trying to "revive" the information in old photographs of documents where brightness and contrast fall off near the edges of the shots.

Thanks all for the responses. I'll try everything and see what works and keep you posted or continue to seek the expertise of all who answered.
You can get an infared digital camera or have your current one reprogrammed to see infared and then use photoshop with various filters to enhance the image. The results are pretty amazing. I took an infared photography workshop at Winterthur a few years go an aw it in action.
Maybe call them and ask to speak to the photography folks there-Al
There are a few tricks to be tried in Photoshop or even in a basic program such as Preview (Mac) Or Paint (Windows). And of course, always work from copies. It all starts with having the highest quality image you can eck out of your camera. Setting the camera to save in high quality Jpeg or even TIFF is the best way to start.

If Jpeg, save the image as a TIFF file to prevent degradation with repeated saves
Desaturate the image, also called making a color image black & white
Invert the desaturated image to bring out details and compare the original and the inverted copy
Back to the original image, in color, play around with contrast and saturation to see if you can bring up the faint elements

Borrow a long wave black light from your local auto body shop and see if that pulls up anything. It depends on what the signature was made with and how it has altered over the decades.

If all else fails, feel free to ask for help. I'ld be happy to work the files over. If they're large, I can give you the url to upload them to.

Hi Ross
If the Photoshop and the black light don't work on their own, what I do to enhance the signature is to add a thin wash of invisible UV Paint or Ink.  If the signature is chalk, crayon or lead pencil this should work fairly well.  A word of caution, don't paint or wipe the solution on, it should be dabbed with a cotton swab or soft cloth.  Lightly dab the area dry and then photograph under black light.  Another word of caution, only do a small edge of the signature to make sure that the solution doesn't dissolve what you are trying to see.  You can buy invisible UV ink or paint at a place called Black Light World or chemical companies if you want to pay more.  Oh yeah, one other thing, if you are walking around the auction houses with your black light, I'm not the only one in history that has done this meathod.  Remember just a small corner to start or test.  Let me know how it goes.  Randy
I have seen many signed pieces. How often would a period piece be signed with chalk or a crayon type material? Just asking could these marks be a later addition? I don't want to cause a problem. We did find one interesting signiture once. His name was Bo Hom
Jeff L Headley said:
I have seen many signed pieces. How often would a period piece be signed with chalk or a crayon type material? Just asking could these marks be a later addition? I don't want to cause a problem. We did find one interesting signiture once. His name was Bo Hom

A very interesting question. I wish I still had access to the JStore research files! I have a suspicion that, given the impermanence of chalk, if the mark is on the underside or back of a piece of furniture, it may very well have been a movers (or teamster) mark of the owner's name. If on a hidden spot, I would guess that the maker would want to use a more permanent form of marking such as colored wax (a crayon like material?) or ink. But that would take some forensic investigation to determine what the material was.

There has to be some research out there that covers this question.

PS... almost forgot this link to the Library of Congress
It's been my experience that if the name is in or on the bottom of the drawer, it is a signature of a past owner. Signatures on the back of the cabinet are either from movers, antique dealers and, if your very lucky, the maker of the cabinet. Chalk or crayons are probably the name of someone who owned the piece at one time. Anyway you look at it, it makes for a good research time. Good luck!
Once again, thanks to all who responded. I have my work cut out to use this panels expertise to help solve my riddle. To clarify further, the signature was clearly written by the builder as they written prior to the installation of the runners and the apron. Secondly, I realized that this wasn't a period piece, but a very well crafted older piece nonetheless. It is still intriguing to follow the clues left behind by a fellow craftsman of another era that started with the toolmarks, oxidation / patina, and led to the 1 - 4  in flowing script on the underside of each leaf to the faintly discernable signature in the same script underneath everything. It's the chase and the practise one gets using the collective skills of all who contributed.  All this fun for $190. at the local antique emporium!