Dressing glass back

Jeff Saylor

Well-known member
Hi All,

I'm in the latter stages of making a Queen Anne Bombe-Front dressing glass, Boston circa 1755 ( pic. from Magazine Antiques).  My question is how were the silvered glasses commonly held in the frames?  Were backs of thin wood usually glued up as a single piece or multiple pieces for controling expansion?  Were they attached directly to the back of the frame or in the rabbet with retaining strips?
Gene Landon just finished teaching a Bombay dressing mirror at Olde Mill (in the Met QA & C book).  The frame is the same as other mirrors - pine with mahogany molding.  The molding overhangs the pine leaving a deep rabbet for the mirror and wood back.  A shallow rabbet on the face of the molding is used for building up the gesso for the gold leaf.

The backs on several 18th century mirrors we saw are one piece; however some were two pieces glued-up.  Almost all had remnants of news print (?) which was apparently applied over the backs to keep dust out.  The backs were held in place with small cut nails.  After seeing all of these old mirrors in class, you have to wonder how they ever stayed together. They reallly are simply built - many with just a miter joint for the frame held together with a couple brads (if that is an appropriate term for a small cut nail)

If you have any ideas were to get "period" looking mirror, please let me know.

Were the backs cut to fit down in the rabbet with the brads nailed to the insides of the frames, or did the backs overlay the frame and brads nailed through it into the back of the frame?
hello Jeff, The mirror's are held in place by small timber wedges, the carcase frame is rabbeted all around its inner back edge,an ogee mould,or champher is on the opposite edge,The mirror is just bedded on thin air?(so the rabbet needs staining before you glaze)  the mirror needs to be 1/4" smaller than the rabbet ,then small timber wedges are glued to the inside edge of the rabbet flush to the back edge,(leave proud untill glue is set,then level off).
the back board is made of 3/8" thick timber, which is 1' 1/4" larger than the rabbet size.
then the back is marked and drilled every 4"around its outer edge, then screwed in place.

So now you have it?a rabbet? filled with 1/4" silver plate glass,held in place by wood wedges,which are leveled to the back edge,and a back screwed inplace.
that's it.
A "rabbet" is a groove along an edge. A "rebate" is something you get after you purchase an item and return the manufacturer's coupon for the "rebate"; that is unless you are a limey.

Howard Steier
Thank you, Tom and Joseph, for your replies.  It's obvious there's more than one way to put a mirror in a frame.  Excellent illustration, Tom.  I already made my frame of mahogany but I like the edge veneered idea.  I think I'll go with your method since I have a 5/8" rabbet (rebate).  Joseph, I had to read your reply twice to understand but I know exactly what you're explaining with the "timber wedges".  That, also, seems to be a good method.

Thanks again.
Howard,  Thanks for the laugh.

Jeff, another thing we saw on these 18th century mirrors was the glass was pretty thin.  Someone pointed out if you put your fingernail against the glass the reflection looks like it comes right from your nail.  Thicker glass would apparently show a gap between your nail and the reflection (Sounds right, but I haven't tried this on a modern mirror).  We didn't see any which had the backs screwed on - all had the backs fit into the rabbet or rebate or whatever it's called.  We may have seen some with the "timber" wedges holding the back board on (in place of the nails) - I would have to check my photos.

Now for a fun story.  After the last class, I had a Philadelphia 18th century Chippendale mirror in the back of my car (not mine).  When I was unloading the car (hatch open) at the owners house, his 120 pound German Sheppard hopped into the back - on top of the mirror!  I had wrapped it in a bed blanket, and had the mirror facing down.  Luckily the mirror escaped without injury.  I however ended up skipping a couple heart beats!

Did the 18th century mirror have any irregularity in the glass surface?  I've used old (1920's) glass but am not sure how "authentic" it looks.
The miror glass was very flat - no waves or bubbles.  Obviously some of the mirrors had that "foxing" (at least that's what I think someone called it) where the mirror looks greyish and does not reflect well.  On some very old mirrors I saw (European - 17th century) the silvering had fallen off in areas.  Since this was at the bottom of the mirror, you could actually see the flakes behind the glass.

I'm attaching some pictures.  Several are the backs of 18th century mirrors - all appear American - based on the molding.  One picture shows the mirror glass.  One shows the dressing mirror we did in class.  One was a small mirror which was solid mahogany; all others had the construction I discussed previously. Hope this helps.


(After attaching the files, the following note came up: "The upload folder is full. Please try a smaller file and/or contact an administrator. ".  If you want the pictures, please send me an e-mail.)