rec.woodworking Ammonia Fuming FAQ
James Roche
Archive-name: woodworking/ammonia
Last-modified: 9/24/97
Copyright (c) 1997 by James J. Roche. All rights reserved.
Ammonia Fuming--Frequently Asked Questions
This FAQ was written by Phil Rose. Please e-mail questions or comments to
pjr...@servtech.com
Purpose:
----------
This FAQ was prepared in response to many requests in rec.woodworking for
information on the ammonia fuming method for coloring wood, usually oak.
Although the method is relatively straightforward and produces uniquely
beautiful results, I hope that no one is encouraged to attempt fuming with
concentrated ammonia before giving serious consideration to requirements
for the safe use of this hazardous material.
Contents:
-----------
Introduction
How does the fuming process differ from staining?
How is the ammonia applied?
What kind of ammonia solution is used?
What is a fuming chamber?
What will I see as an indication of color formation, and when?
What sort of fuming time is needed?
What safety precautions are necessary?
Is it best to fume the piece before or after final assembly (gluing,
sanding, etc.)?
Is the fuming color effect permanent?
Other sources of information, please?
Introduction:
---------------
G. Stickley published the following legend about the origin of ammonia fuming:
"Some oak boards stored in a stable in England were found after a time to
have taken on a beautiful mellow brown tone and on investigation this
change in color was discovered to be due to the ammonia fumes that
naturally are present in stables."
[Gustav Stickley, in "Craftsman Homes" (1909)]
According to Gustav Stickley, this (color formation) phenomenon first
became understood after work was done in his Craftsman Workshops which
showed that the dark color was "due to the chemical affinity existing
between ammonia and tannic acid of which there is a large percentage
present in white oak." Consequently, other tannin-containing woods such as
cherry and chestnut could also be fumed, but the "fuming" process is
commonly done only with oak.
For pieces in the Arts and Crafts style, the use of white oak and ammonia
fuming gives an authentic look, although certainly stains were employed by
Stickley and others during the A&C period. It should be noted that the
fuming treatment does not "finish" the wood, but merely changes the color
to a deep brown tone. Application of a clear penetrating (and/or surface)
finish is required as the final step, to give protection as well as
significant color depth .
Q. How does the fuming process differ from staining?
======================================
A. First, the brown color is produced by reaction with ammonia vapor and
requires no contact of any liquid with the wood (other than an application
of clear finish, later ). No brushing, streaking, dripping, dipping or
wiping is involved. Second, the fumed color often extends much more deeply
into the wood (especially in comparison to solid-pigment stains), and depth
of coloration can be as much as several millimeters (1/8"). Furthermore,
with quartersawn oak, the ray-fleck features are colored by the fumes yet
retain a muted contrast with the rest of the wood, yielding results
distinct from the high contrast produced by a solid-pigment stain. Finally,
unlike staining, ammonia fuming offers a limited range of color(s).
Depending on the duration of fuming and the wood properties (tannin
content) the color can range from light brown to chocolate brown/black.
Since there can be sapwood/heartwood variations in tannin level, the
intensity of the developed color may show some variability (as can happen
with stains) which is minimized--but might not be eliminated-- if the piece
is constructed using wood from a single tree. Color intensity variations
resulting from fuming may be further minimized by subsequent touching up
with stain or by direct application of ammonia solution to the lighter
parts.
Take care not to overdo the fuming, inasmuch as the depth of color (i.e.,
penetration) will make it nearly impossible to correct. Err on the side of
"too little", as it's easy to resume fuming to intensify the color.
Q. How is the ammonia applied?
========================
A. The most common procedure is to place the workpiece(s)in a well-sealed
enclosure, such as a plastic box, a can or a tent of polyethylene
sheeting). Then you place one or more small containers of ammonia solution
on the floor the tent. An alternative is to brush the wood directly with
ammonia solution, but this has the disadvantage of grain-raising and
prolonged exposure (of yourself!) to ammonia fumes. However it is said to
be practical to do touch-ups by direct application of ammonia solution.
I've found it convenient to pour a small amount (i.e., 4-8 oz) of ammonia
solution into a wide-mouth glass jar with a tight-fitting screw-on lid. I
place the closed jar (one or more) into the tent and when everything is
arranged and the tent opening is ready to be taped or clamped shut, I reach
in, remove the lid(s) and then quickly seal up the chamber. With a little
planning and care, you can avoid significant exposure (of yourself) to the
fumes during these steps. As mentioned below, a modest-size electric fan
could be helpful to direct the fumes away from you while filling the
container(s) and doing the final enclosure seal-up.
You should not be able to detect a strong ammonia smell from any modest
distance (say 5-8 feet) if the enclosure is properly sealed. However, some
ammonia odor will be present right at the taped or clamped seams in most
cases. This is not likely to be a problem since the procedure is only to be
done outdoors.
Q. What kind of ammonia solution is used?
======================================================
A. To do fuming efficiently, it is necessary to use a very concentrated (26
% by volume) solution. This may be obtained in one gallon bottles at
blueprint (drafting) supply shops. Chemical supply outlets also ought to
have this strength available. While it is possible, theoretically, to use
the *much* weaker household ammonia (about 5%), extremely lengthy fuming
times would be needed. (see below)
Q. What is a fuming chamber?
=======================
A. Well, it's anything that can do the job, which means it's big enough to
contain the workpiece, but not excessively large and it must be readily and
completely sealed (including the bottom). I've made enclosures starting
with a lightweight frame made of 1x2 pine (twelve edges, open sides,
fastened by a handful of drywall screws). The box frame is completely
wrapped (around one axis) by a single sheet (if possible) of 4 or 6 mil
polyethylene. The wrap is started by stapling one edge of the sheeting to
an edge of the frame. The wrapping material initially is cut so that it
will extend several feet beyond each "open" end of the frame (think of
gift-wrapping a package). Duct tape is used to seal the only seam, which is
along the long axis (assuming you're not making a cube). If you ensure
there is adequate "extra" poly to extend well beyond each end, it can be
taped and/or rolled up and clamped tightly shut with numerous spring
clamps, heavy-duty clothes pins, etc.
Another approach would be to cut separate sheets of polyethylene and to
attach these (by stapling) to each side of the frame. Use duct tape to seal
each seam.
Introduce and arrange the workpiece (or its parts) through the opening of
the box; then when you are ready to close and quickly seal up the open
side, place (on the floor) inside one or two small dishes (p referrably,
widemouth jars) of ammonia solution . Remove the jar lid(s) and seal up the
opening. Even a large chamber should need no more than about a pint (total)
of solution. There is little harm in using too much solution--other than
the effort needed to reclaim the liquid for later use (or disposal).
For small pieces like a lamp base (clocks, boxes, etc.), it is possible for
the fuming enclosure to be merely a heavy-duty polyethylene yard (lawn)
bag. A plastic can (e.g., garbage can) could be used inside the bag to
provide some extra stability. To fume a 20"-high lamp base, I placed the
piece inside a plastic garbage can (probably 15 or 20 gallons) along with a
small jar of ammonia solution. I was then able to enclose the can within a
40 gallon lawn bag. After the jar of ammonia solution was opened, the top
of the bag was tightly rolled up and sealed with several spring clamps and
a couple of wooden battens to distribute the clamping force.
A well-sealed chamber is important because: (1) leakage could cause
discomfort in the vicinity (and possibly be a hazard to neighbors), and (2)
any major leaks could make it necessary to use very long fuming times (or
produce unpredictable effects).
Q. What will I be able see as an indication of color formation, and when?
================================================
A. Actually the wood will respond fairly soon (within a few hours) by
taking on what I find to be a dull, gray-brown caste. This tone will
intensify with increased fuming time, but it is only a raw (unfinished)
state, which is not much like the chocolate brown or even dark reddish
brown that can be achieved by fuming. But don't despair at the dull
unintersting color you may see at first; as the rich, final color will not
be evident until you apply a clear "finish" such as a penetrating oil or
varnish (or just use a wipe of mineral spirits in order to test the
progress of the workpiece).
So, to repeat: evaluate the color achieved by removing a test piece (see
below) from the fuming chamber and apply some oil (e.g., Watco) or mineral
spirits. This fact often is not grasped by beginners, who fume the
workpiece--perhaps extensively--and then give up in frustration after
seeing only the "raw" effect.
Q. What sort of fuming time is needed?
=============================
A. It requires some preliminary trial-and-error testing to determine
optimum fuming time(s). This is best done with cut-offs from the same wood
used in the piece to be treated. A suggested approach for testing is to
treat several (or more) similar small test pieces which can be removed at
intervals--one at a time--and oil applied to them for evaluation. Care is
needed here to avoid breathing fumes as you remove each sample and reseal
the enclosure (see Safety Precautions). Given three test pieces, you might
wish to pull one out at intervals such as 4, 15 and 24 hours, respectively.
The necessary time can depend somewhat upon the relative tightness of the
fuming enclosure. A well- sealed chamber naturally is most efficient. Some
color (possibly the desired intensity) can result from as little as a few
hours of fuming, while deeper color will usually be produced after periods
of 10 to 24 (or more) hours. With dilute household ammonia, expect the
fuming period to be many-fold greater. Ambient temperature will play a
role; colder temperatures will slow the process. Also, don't forget you're
producing a 100 %RH environment in the fuming chamber, so...condensation
could take place inside the tent if overnight temperatures drop
significantly.
Q. What safety precautions are necessary?
===============================
A. It is important to be aware of the hazardous nature of concentrated
ammonia and to treat the liquid and its vapor with great care. Never
attempt to enter a large fuming chamber before covering the ammonia
containers and then allowing fumes to dissipate. At low fume levels (not
particularly dangerous or permanent-damage inducing) ammonia will be very
irritating and choking, and hence, will provide an adequate warning sign
that you should reduce contact as quickly as possible.
NOTE: Concentrated ammonia is very caustic and can cause burns to the skin,
eyes and mucous membranes if fumes are deeply inhaled or the liquid
contacted. Warnings and emergency treatment procedures are on the label.
Read them! Use gloves and eye protection (goggles).
Even with good ventilation, I'd advise the practice holding a deep breath
while handling open containers of ammonia solution, and by all means verify
that you can do so for the length of time needed (1) to pour out the
solution into smaller containers and (2) place them in (or remove from) the
chamber. Unless the chamber is small and the open containers of ammonia are
within easy reach, you should verify that you have some means--such as
long tongs -- to cover and /or withdraw the container(s) without encountering
an objectionable level of fumes. I don't use a respirator, but I would do
so if I intended to do fuming on a regular, frequent basis. A good idea is
to use an electric fan to direct the fumes away from you while opening the
ammonia container and pouring out liquid or while opening the chamber to
remove the workpiece after the fuming is completed. After removal from the
chamber, fumed wood will require 1 to 2 days of airing to lose most of the
ammonia odor. I usually apply finish coats (oil) after 2 days.
Note: NEVER carry out the fuming process in a closed room! Only work
outside (or in a detached garage/shop), away from open doors and windows.
If the fuming chamber is within an attached garage, be certain to keep the
outside garage door fully open during the entire procedure. Make sure
inquisitive pets, small children, etc., are kept away.
Q. Is it best to fume the piece before or after final assembly (gluing,
sanding, etc.)?
=============================================================
A. My practice has been to assemble & glue all joints and to do final
finish-sanding before the piece is fumed. Significant grain-raising does
not appear to occur as a result of fuming, although keep in mind that the
fuming chamber is a high-humidity environment.
Drawers should be pulled completely out, and tabletops can (should?) be
detached to promote complete coverage. Make certain all areas to be colored
are fully exposed; the undersides of boards will be fumed OK as long as
they are not in contact with the floor or other objects. As with staining,
glue residues need to be carefully removed beforehand, but it seems that
the effect of glue residue is not quite so severe as with staining
(probably glue residue has little effect on ammonia penetration/reaction,
but prevents the final clear finish from reaching the wood and producing
full depth of color.) Some people prefer to fume all pieces before
assembly/gluing. As far as I know, if fuming is done first, it will not
interfere with gluing later on.
Q. Is the fuming color effect permanent?
===================================
A. Yes, as far as I know. Pieces fumed nearly 100 years ago seem to have
maintained color. But of course, who knows what they looked like back then?
Q. Other sources of information, please?
==============================
A. Several fairly recent publications come to mind:
Gene Lehnert, "Craftsman Style Comfort in a Morris Chair", Fine Woodworking,
No. 101, pp. 41-42 (1993)
Joseph J. Bavaro and Thomas L. Mossman, "The Furniture of Gustav Stickley",
Linden Publishing Co., Fresno, pp. 84-87 (1996) ISBN 0-941936-35-X.
This excellent resource presents very useful information on construction of
Stickley-style furniture. A very questionable part of their fuming
technique is the lack of a sealed floor in the fuming enclosure shown in
the photo-illustrations.
Kevin Rodel, "Fuming with Ammonia", Fine Woodworking, No. 126, pp. 46-49
(Oct. 1997). This is the best illustrated article I've yet seen, with very
useful photographs to indicate the range of tones achievable by this
method. He also shows some results for woods other than white oak. A
must-read article.
Phil Rose
June 1997
**********************************************
* Phil & Judy Rose E-mail: *
* pjr...@servtech.com *
**********************************************
--
Jim Roche
ro...@cs.rochester.edu
University of Rochester Computer Science Department Rochester, NY 14627