*********************************
Workshop Hints
Bluing hints
http://www.bhi.co.uk/aHints/bluing.html
The British Horological Institute has archived and edited the
following from e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not
necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves
whether the methods listed below will suit them.
from:
Ray Bates, Steven Berger, Steve Callihan, Jacques Le
Clainche, Scott Fuller, Tony Gray, Harry Gilmore, John Haddy, Alan Heldman, Eliot Isaacs FBHI, Mel Kaye, John C. Losch, Mike
Murray, W. R. Smith, Tim Sweet.
Index
General
Preparation
Bluing
Touching up afterwards
Pseudo Bluing
HYPERLINK "http://www.bhi.co.uk/aHints/bluing.html"
\l "Bluing Screws"Bluing screws
General
Some of the methods are very dangerous and should only be undertaken
with extreme caution. All the methods use heat and will give off some fumes. These methods should only be used in a well ventilated
area and away from any younger persons who may get hurt. The BHI does not endorse any one method of bluing hands, but suggest
you try some of these methods to find which one suits you best.
Many clocks and watches that come into the workshop for repair
have blued hands that are not in as good a condition as they could be. It is, with practice, quite a simple job to re-blue
the hands again. The process involves cleaning the old hands and then heating the hands until they are the right colour.
If the rust on your hands is only superficial, try placing them
on the bench and scrubbing them with a steel brush (hardware store variety, fine wire). It will remove the rust and leave
the basic heat blued original finish. A coating of oil or wax will make them look good and help to inhibit further rusting.
However if the rust is more than superficial, you will need to undertake the following.
Preparation
It cannot be emphasised enough that the final finish depends
on the amount of polish and finish you put into the hands before you blue.
If you are re-bluing existing hands and the hands are old and
rusted, first remove the rust by placing them on a piece of pith wood with the tube pushed down into the pith wood to hold
them in place and remove the rust. You can use soap stone, or they can be buffed with extreme care or diamatine (diamond dust)
and oil on a hard wood stick flattened on one side.
To avoid the need for polishing away the blue to obtain the
bright polished finish required for a good blue job, you can boil the hand in a mixture of boric acid and water. This will
remove the blue without the need for abrading it away. Also, quite often the finish remaining is good enough that re-polishing
is not required, or at least minimised. Be sure to remove all wax before boiling.
When making a new hand , it is best to avoid the use of tool
steel. It often contains elements that prevent bluing by heat. A simple heating of a test piece of the material will save
a lot of wasted work. Also, when making a hand, one sometimes gets a poor result and needs to start the bluing process over
again. Of course, the quality of the blue obtained is very dependent on the polish and cleanliness of the hand before bluing.
When making a new hand, I usually go from a file, through the emery grits from 320 to 600, followed by buffing with Tripoli
and rouge, then a solvent to remove the grease of the polishing compounds. At this point one is wise to use cotton gloves
to prevent finger marks. I once had a pair of dirty tweezers ruin a blue job.
Bluing
If you want to do the job properly, heat bluing is the route
for you. But, be prepared for a lot of practice and frustration. The thinner the metal you are working with or the degree
of taper from boss to tip that you are bluing, the greater the difficulty.
Too much heat, and you will "white out" the steel, and will
have to start all over. Not enough movement of the heat source according to the thickness of the hands and you will vary the
colour from too light to deep blue to purple, to brown. Whenever you "white out" you have to polish the steel down again,
and start over.
Method 1.
This method involves placing the hands on a bed of granules
that will transmit the heat evenly over the whole length of the hand.
Place granules (silica sand, Salt or Clean Brass filings) in
a tin or metal type pan. Use about 1/8" of granules in pan. Lay the hands finish side up on the sand and with heat source
of some kind such as a wood oil burner, begin heating the bottom of the pan and keep the pan moving with the hands staying
in the centre of the flame as much as possible. After the sand gets hot the hands will begin to change colour - a reddish
colour first and a maroon colour and then watch carefully for the colour you desire. When the colour is as you please, remove
the hands and place in water or oil to cool.
NOTE: Some people use molten Lead or Hot Oil instead of granules.
Be aware that hot liquids can do more damage to you than hot metals if you should accidentally tip them over yourself (or
worse someone else!)
Method 2.
Use a hot air gun, you know the sort of thing that’s used
for stripping paint. With a little practice (very little, I might add) this gadget enables almost perfect control of the process.
By varying the distance of the nozzle from the hand (which is placed on a heat resistant fibre board) it is easy to progress
slowly through all of the colours until a nice even blue is obtained. Initial preparation of the hands is of course the same
as for any other method of bluing.
Method 3.
An electric tempering oven with a pyrometer and temperature
control enables you to set any temperature in the range of colouring or tempering steel. By putting the hands in the oven
and then letting them come to temperature, they will blue themselves. It is also useful for tempering pinions and other clock
parts, for annealing arbors to be drilled, and for some kinds of soldering, etc.
Method 4.
For cheap clocks where the full heat bluing process would be
an overkill, strip them and use selenic acid, obtainable as gun blue under the trade name (Formula 44/40) It gives a blackish
colour, acceptable in cheap clocks whose hands were probably finished similarly, and will last with a faint coating of oil,
wax or lacquer
Touching up afterwards.
When bluing on brass shavings, or clean sand, some parts of
the hand come-up more quickly than others. The lagging portions can often be brought up to the same colour as the darker parts
by either of the following 2 methods.
Method 1.
Using a slightly curved piece of 1/4" X 1" brass strip. It can
be clamped to a stand over either a controlled Bunsen burner flame or (for a long time) over an alcohol lamp. The area to
be blued can be rubbed over the heated brass while the hand is held in tweezers. As colour progresses move the hand along
starting at the thickest or widest part and moving to the thinner areas in need of repair.
Method 2.
By waving the pinpoint flame of a small torch across the lagging
part. "Wave" is the secret. Just one fast pass across the lagging area and wait, then another and wait, etc.
Pseudo Bluing
It is possible to simulate bluing for clocks and watches that
do not justify the cost of proper bluing.
The substances available are:-
Blue enamel (sold for the purpose),
Gun bluing paste
Super Blue Extra Strength Gun Blue For Steel
Brownells Oxpho-Blue (USA)
Parker Hales's Comet Super Blue.(UK)
Note: The above contain various acids including the poisonous
Selenious acid.
Paint
Made in the U.K. called Citadel Colour and its colour
is deadly nightshade. Brush an extremely small amount on and I doubt that anyone could tell that it was retouched. I'm confident
that if any blued hands needed repair and I needed to hide a small amount of Tix solder, that this combination will do the
job nicely.
I think the Citadel range are of a similar formulation to artists' acrylic colour, with some being opaque and
others (perhaps "deadly nightshade") translucent.
The firm Citadel Miniatures AKA Games Workshop Inc. is UK based, The
addresses that I have for the companies are:
Games Workshop Ltd, Chewton Street, Hilltop, Eastwood,
Nottingham,
NG16 3HY, U K
Tel: (01773) 760462
and
Games Workshop Inc., 3431 C Benson Avenue, Baltimore,
Maryland, 21227-1072,
U S A
Tel: (301) 644 5699
A selection of marker pens
"edding 800". It is more opaque
and a better colour than other markers that I have tried, and the result is not as black as gun blue. The only problem that
I encountered was that it did not dry very hard, and was prone to fingerprinting. A satisfactory solution is to let it dry
and then quickly brush on a coat of auto acrylic lacquer -- this results in a hard durable surface. Make sure you clean your
brush well afterwards as some of the blue colour will almost certainly have been picked up.
'layout blue'.
A quick swipe of the felt tip covers any
piece of metal, brass or steel, with a bright blue
coating, which dries instantly, and shows lines made by a scriber with
superb clarity - far easier and more convenient to use than old fashioned marking fluid.
A couple of words of caution - there are two versions of these
pens - water based and spirit based, and it is the latter which is useful. The spirit dries out very quickly, and it is essential
to keep the cap tightly on when not in use. I store mine upright, cap down, and this seems to make them last longer. After
the work is complete, all traces of the blue are easily removed with methylated spirit (denatured alcohol). We use these markers
on a regular basis in the BHI seminar workshops.
Bluing Screws
To blue a screw head you first have to clean it up, polish it,
and then remove any oily or greasy deposits from the surface.
holding the screw (by its thread) in a pin vice or lathe; cleaning
the slot with a piercing saw or junior hacksaw; removing any burr with a pivot file
polishing the head on a piece of crocus paper or 3/0-emery,
supported on a cork or other flexible sheet.
When the polish is to your satisfaction, wash it off in meths,
alcohol, or other volatile solvent.
Then, holding it by the threaded end in a pair of old snipe-nose
pliers, slowly pass it in and out through a spirit lamp flame. Watch very carefully for the straw colour beginning to appear
and continue until there is a nice deep purple. By this time, with a little experience, you would already have the screw withdrawn
from the flame.
As soon as the colour is right *immediately* quench the screw
in water, dry it and rinse again in solvent.
Complicated? -- the whole operation would probably be completed
in less time than it took to read this paragraph, and it is FUN.
If you have a *whole batch* of screws to get to exactly the
same colour, take a piece of thickish brass plate, drill a number of holes clearance size for the screw thread in it, and
drop a screw into each hole.
Heat the whole plate, screws and all, over the alcohol lamp, then when the right colour is
reached (or just a smidgen before), upend the plate and tip all the screws simultaneously into cold water. I dewater the screws
in white spirit, then dry (with a soft tissue, not a hot air gun - this could change the colour), and give a final wipe with
thin oil to bring up the blue colour to its gleaming best, and stop any future rusting.
***********************************
