Full Chisel Blog

November 9, 2011

Putty is your buddy.

With all the talk of nailed furniture, you will need something to fill those nail holes plus any cracks, voids, knots and other irregularities.  And the traditional method of making putty is very simple: boiled linseed oil and whiting [calcium carbonate or chalk] mixed to the consistency of putty.
I use stand oil or sun thickened linseed oil together with some regular boiled linseed oil to help things dry quicker, see Shellac, Linseed Oil, & Paint – Traditional 19th Century Woodwork Finishes for more details.  I will sometimes mix the calcium carbonate with Moses T’s St. John’s Oil which has turpentine that helps in the drying.

This is some putty I mixed up for the exterior woodwork for the Fairbanks Homestead [1850’s building] as well as on the patterns I have been recently working on.
This works great as putty for an oil paint finish, you can carefully paint over it right away and it will dry under the oil paint.  Other surface finishes require that the putty dries which can take from a day to a week depending on the conditions of temperature and humidity.  It eventually becomes very hard yet remains flexible for wood movement.  It does not shrink when it dries.

Another putty can be made with thinned Hide Glue and wood flour, saw dust or calcium carbonate and it acts like the water based putty but is a bit stickier and adheres better to smooth surfaces.  See Hide Glue – Historical & Practical Applications for more details.
If you can’t wait for the oil/chalk to dry then you can use calcium sulphate [gypsum or plaster of Paris] and water to the consistency of putty.  I also add some whiting to thicken or sometimes wood flour [very fine sawdust] if the holes are large.  Repeated applications are required as it will shrink as it dries, but once dry is very stable.  Also a drop or two of glycerin will keep it flexible if necessary.
The application for each is slightly different, the oil based putty can be applied using a putty knife then smoothed with the fingers, the stuff is quite magical when you work with it for a while, and you’ll see how nicely it behaves.  The water based putty needs to be worked with a putty knife quickly before it sets up; its open time [before it sets] is short and needs to be smoothed before it dries.
With each of these putties, dry powdered pigments can be added to color the putty to match the color of the surface of the work.  The oil/whiting putty can be colored with artist’s oil colors and the water/plaster of Paris can be colored with artist’s water colors, I prefer the dry powdered pigments because they are dirt cheap.  Oh wait they are dirt.
The oil based colored putty will dry the color it is when mixed up, the water based colored putty will dry a lighter color than when mixed up, so some experimentation might be required.  I try to get the putty a slightly lighter value of the color as it doesn’t stand out as much as if the putty is too dark.
Putty is nothing new in woodworking some sarcophagi from ancient Egypt show the early use of putty.  Fill the lacuna.
Stephen

2 Comments »

  1. Hi Stephen,

    Can the oil-based putty be sealed up and kept on a shelf? I expect a baby-food jar would hold more putty than I’d use in a year. Also, would you use something like Stanley’s chalkline refill chalk, or a different grade? I have some powdered chalk from my rock climbing days, but I suspect it’s MgCO3 rather than CaCO3 (and I’d rather not use it for putty, anyway).

    thanks,
    Adam

    Comment by Adam Maxwell — November 9, 2011 @ 11:43 am

  2. Adam,

    Yes it stores well, a bit of the oil floats up and provides a barrier. It will skin over but if you keep it mixed regularly it will last for some time. I try and mix up just enough for the job at hand but do end up with some left in a jar.

    I don’t know the composition of chalk line chalk, whiting can be purchased at a good paint store or pottery or ceramics supply houses.

    Stephen

    Comment by Stephen Shepherd — November 9, 2011 @ 12:58 pm

RSS feed for comments on this post. TrackBack URL

Leave a comment

Powered by WordPress