By Bill Gerrey
This overview of blind soldering techniques was adapted by Josh Miele for use from Soldering, Part II, By Bill Gerrey, originally published
in the Smith-Kettlewell Technical File, Volume 2, No. 4, Winter, 1981. The
original article included extensive product references, suppliers of equipment,
and pricing, many of which were out of date and have been omitted in this
adaptation. The present version of this article was developed as background
reading for a Blind Soldering Workshop offered by the LightHouse for the Blind
and Visually Impaired of San Francisco, and the Smith-Kettlewell Rehabilitation
Engineering Research Center, November 4-6, 2016.
Forming a Solder Bond
The principles of forming a solder bond can be summarized as follows:
- Molten solder acts as a solvent--it dissolves metal from
the surface of the pieces being joined, forming a bridge of alloys from
one metal to the other.
- All the metals being joined must reach the "alloying
temperature" in order to be soluble in molten solder. The metals must
be in firm contact with each other so that they all reach this alloying
- Heat transfer from the hot iron to the joint of the
metals must be extremely efficient to afford good soldering and to
prevent damage to connected components of the work. If the transfer of
heat is done inefficiently, a long time will elapse before the adjoining
metals reach the alloying temperature; during this time, considerable energy
will be absorbed by the components and damage may result.
- In order for heat to be efficiently transferred to the
metals from a hot iron, a complete metallic path must be established
between the iron and the work. In fact, the iron itself must be involved
in the continuity of alloys. The iron and the metals being joined must
all have their surfaces in solution with the molten solder; this is known
- Oxides on the metallic surfaces prevent wetting by the
molten solder; the solder cannot reach clean surface metal to alloy with
it. Furthermore, oxides build up very rapidly at high temperatures,
insulating the hot iron from the work. A chemical "reducing
agent" known as flux, must be applied to all the surfaces during
soldering to strip these surfaces bare of oxides, allowing the formation
of pure metallic alloys.
- Rosin Flux (used in electrical soldering) is a fairly
active reducing agent when heated, but remains inert at temperatures below
soldering temperatures. Its resistance to chemical interaction after the
solder has cooled makes it ideal for electrical work; its residue is
- Given ideal conditions, soldering is done in the following
manner: The tip of the hot iron is put in contact with all the adjoining
metals. Flux-core solder is put in contact with the work and the tip of
the iron which causes a column of molten solder to flow between the iron
and the work. After this initial melting of solder, the application of
additional solder should primarily be fed to the work pieces and not to
the tip of the iron. Solder which is applied to the iron alone and which
subsequently runs down into the work will generally not involve itself in
bonding. Its flux will be used up cleaning the iron and not the work; it
will not be able to get through the oxides onto the bare metal surfaces.
Feeding solder to the work alone maximizes the effectiveness of the flux,
and provides a good indication as to whether or not the metals being
joined have reached soldering temperature.
Continuous - Heat Soldering Irons
Much of what follows is a clean break from theory; it is a highly subjective
discussion of the techniques I use when soldering with a continuously hot iron.
Many of the statements to follow are refutable. Take each stated technique as a
seed from which you can "grow your own".
There are two basic classes of continuous-heat soldering irons, simple
garden variety constant-power irons, and "temperature-controlled"
Constant-power units are comparatively inexpensive. Their heating element is
a simple power resistor which is energized continuously. Their main
disadvantage is that while they are not in contact with a work piece, they must
dissipate all their heat energy in free air, which means that they reach fairly
high temperatures between soldering operations. Their tip temperature may
approach 1,000 dg F, (about 450 dg C) while the iron is in the rest stand. To
protect the "tinned" surface of the tip from oxidizing, at these high
temperatures, it is crucial that fresh solder be always present on the tip.
Temperature-controlled irons are those which have
"thermostatically-controlled" mechanisms for sensing and maintaining
the temperature of the tip. With these units, the temperature is held to a
specific value, whether the iron is in use or at rest. Typically, these irons
are designed to maintain a tip temperature of 650 dg F (about 350 dg C).
The tip of a temperature-controlled iron is not subjected to heat cycling
over a wide range of temperatures, and the overall tip temperature is lower
(more than 300 dg lower). These features give rise to a longer tip life. In
addition, the likelihood of a solder joint reaching a very high temperature,
which can damage the flux, is minimized. Finally, the 30 percent reduction in
tip temperature may be slightly less injurious to the fingers, if the job is
such that the tip must be frequently touched. (In all fairness, it should be
stated here that Dennis Bernier, Vice-President of Research and Development at
Kester Solder Company, prefers a well-designed constant-power iron over
temperature-controlled ones. He argues that a well-designed constant-power iron
is able to maintain a fairly constant temperature, and that
temperature-controlled irons can often subject the work to electrical
transience as they switch on and off. He also recommends that when choosing a
temperature-controlled iron, obtaining one with a tip temperature no lower than
700 dg F is preferable for efficient heating of the work.)
When choosing a soldering iron, pick one with a high power rating, so that
it can supply heat energy to the localized area of interest at a much faster
rate than energy can be conducted away from the connection by components of the
work. Small-sized, lower-power irons are made for specialized applications,
such as miniaturized assemblies on which larger irons cannot be maneuvered into
position. (1 used a 25 watt iron for years, only to find out that components
were absorbing enough heat energy to be damaging, while I shifted from one foot
to the other waiting for the solder to melt). The iron should be as large as
can practically be used, given its physical size and configuration.
Unless they are a very small size, temperature-controlled irons are designed
to supply high levels of heat energy when they are called upon to do so. When
the tip temperature drops below their specified value, a high amount of energy
will be supplied by the iron until the tip temperature is restored to the rated
Constant-power irons, on the other hand, only have their given
power rating available for transferring heat energy to the work. Ideally, given
the size of electronic components used in most assemblies, an iron of 50 watts
or more enables the user to make connections quickly and efficiently. However,
for the blind technician, irons of this power rating may have unfavorable
physical characteristics; they are often very long, and their heating element
may be comparatively large in diameter. The blind technician may wish to
compromise on the power rating to obtain an iron of smaller physical size. I
recommend not using irons of less than about 35 watts.
Key Physical Parameters
By picking an iron with certain key physical characteristics, you can
optimize your accuracy and stability in performing the task of soldering.
The length of the hot portion of the iron (from the handle to the
tip) should be as short as possible, so that your sense of the tip position can
be accurately predicted. The iron becomes an extension of your hand; the
position of your hand and the angle at which you hold the iron are valuable
pieces of information which you must use to predict the tip's location. The
shorter the iron is, the more meaningful will be this information.
By the same logic, the handle of the iron should be well enough insulated
from the heat to afford holding the handle at its extreme forward end.
The diameter of the "barrel", which is the heating element, should
be as small as possible to minimize the likelihood of its contacting nearby
wiring or your other hand.
It is my experience that a great advantage in stability can be gained from
choosing a tip which has flat contact faces. In contrast to this, the tip style
which has gained overwhelming popular acceptance is conical in shape; it has no
flat contact face. When holding a conical tip against the work, the contact
force must be exactly perpendicular to the surface of the cone, otherwise the
iron will tend to slip or "glance" off the connection. In other
words, holding a round tapered tip against a work piece is difficult, and is
subject to instability. I have found that by using a tip with flat contact
surfaces, "glancing" of the iron off the work is less of a problem.
Replacement tips which have flat contact faces are available for almost any
make of iron. In general, three such tip styles are available from soldering
iron manufacturers - pyramid-shaped, chisel-shaped and screwdriver-shaped tips.
(Incidentally, all these styles have far better heat conductivity than does a
tip of conical shape). Screwdriver tips are the most suitable for electronic
assembly, since they are usually thin enough to fit between closely spaced
terminals. Whichever style is chosen, the handle of the iron should be marked
adjacent to each flat surface, so that the tip can be properly oriented with
respect to the work. The handle can be marked by filing notches into it, or by
attaching narrow strips of Dymo tape along it.
Care and Feeding of the Soldering Iron
A soldering iron is a very vulnerable instrument. Operating at extremely
high temperatures, the iron can supply enough heat energy to promote a variety
of "endothermic" chemical reactions, all of which are detrimental to
Since the surface metal of a soldering iron tip is chemically active, it is
prone to oxidation; and this tendency is greatly accelerated at high
During idle periods, the heat of the iron can carbonize any flux residue
present on the tip.
The iron may accidentally come in contact with foreign materials which melt
when subjected to its intense heat. Some notable examples are plastic building
materials, insulation on the wiring, painted surfaces, and insufficiently damp
cleaning sponges. If deposits of such foreign matter melt off on to the tip of
the iron, they quickly carbonize and cling stubbornly to the tip.
Any soil on the tip acts as a heat insulator, and it renders the iron
incapable of effectively heating the work. The only protection the iron can
have against this soil is to be kept wet with solder. Since the surface metal
of the tip will not be exposed to the atmosphere under these conditions,
oxidation of the tip metal itself will not occur. Any carbonized residues will
tend to "float" on top of the molten solder, thus protecting the tip
itself from contamination.
Therefore, a solution of molten solder must always be kept present on the
tip of a well cared for iron. The solder-wet tip can easily be wiped clean on a
damp cleaning sponge, but this procedure should be followed soon after with the
application of fresh solder to the tip.
In the normal sequence of making solder connections one after another, the
tip of the iron is kept reasonably wet automatically. However, an occasional
"slap-dash" application of solder to the tip assures that voids in
the surface solution do not go untreated; a good bath in fresh flux will strip
oxides and other contamination off the surface metal. Initially, of course, new
tips should be bathed in fresh solder before being used.
Special mention should be made here regarding the simplest of tips, those
which are made of bare copper. Copper is extremely soluble in solder. Copper
from these tips is actually dissolved into each solder connection; these tips
eventually become pitted and worn away. They can be redressed by filing or
sanding them down to a smooth new surface, at which point they must be treated
as a new tip. Never attempt this redressing procedure on steel or
iron-clad tips (see "Soldering", Part I).
"Tinning" the iron specifically refers to applying a coat of fresh
solder to the tip. This can be done in two ways. If the iron is cold, wrap
about three inches of solder around the tip and turn the iron on. (To some
people, these three inches may seem like an excessive amount of solder, but the
point is to assure that the entire surface of the tip is bathed in fresh
solder. Overdoing the amount harms nothing.) If the iron is to be
"tinned" while hot, solder must be "brushed" along the tip.
To make sure that the entire tip is being bathed in fresh solder, turn the iron
slowly while "brushing" the solder over the tip.
Finding the tip of a hot iron with a piece of solder is no easy task.
To aid in doing so, rest both hands against some familiar object, such as
your vise or the rest stand, so that you have some idea as to where the iron
and the piece of solder will intersect. I often extend the piece of solder an
inch or so beyond my projected point of intersection, thus allowing the iron to
"cut" the solder to the exact length.
Do the "tinning" procedure over an unimportant surface which is
not flammable. It is a good idea to "tin" the iron over a wet
cleaning sponge, but remember to retrieve the solder droplets from the sponge;
they will be larger than those left in the sponge after normal wiping, and you
do not want the iron to pick them up later.
The iron can be cleaned by wiping it on a wet cloth or a wet cellulose
sponge. Whichever you use, the item must contain nothing which will contaminate
the iron. For example, no cloth having components of polyester are acceptable.
Also, many general purpose cleaning sponges contain chemicals which can soil
the tip. Above all, the item used must be wet (dripping wet is
acceptable). This is essential, since while the iron is being wiped free of its
protective excess solder, it is very vulnerable to charring foreign matter.
Sponges designed for this purpose are available from various soldering
equipment manufacturers. The best cleaning sponges are those which envelope or
surround the tip when it is being wiped. These sponges can either be convoluted
(being made up of lobes), or they can be comprised of a "sandwich" of
separate sponges standing on edge. With simple flat sponges, several passes
must be made (rotating the iron between each pass) to assure that the tip has
been wiped on all sides. This tends to cool the iron more than is done by
making a single pass through a sponge of complex configuration. (For the blind
technician, it is vital that all droplets of excess solder be removed, since
they can cause serious burns. Dennis Bernier of Kester Solder Company pointed
out to me that wiping the tip on a simple flat sponge tends to transfer
droplets to the unwiped side of the tip, and does not assure that they will be
removed.) Wipe the iron immediately before soldering. After soldering has been
accomplished, return the iron to its rest stand; do not wipe the tip
free of excess solder at this time.
Many accidents can happen to damage the iron. All of these accidents are
preventable if reasonable steps are taken.
The power cord of the iron should be kept off to one side at all times to
prevent the iron from coming in contact with it. In fact, all cables should be
kept well out of the way, even if they do not pose an immediate electrical
hazard. If the tip of the iron comes in contact with any such cable, it will
become contaminated with very stubborn soil.
Plastic handle tools should be kept clear of the rest stand to avoid being
grazed by the tip, resulting in its contamination.
Finally, the tip should not be banged into things which can mar its surface.
To avoid striking the tip on sharp corners and edges of the rest stand,
carefully note the position of the rest stand so that you can approach it
slowly and gracefully with the iron.
Handling the Iron
This section covers a lot of territory - practice reaching, establishing
well-defined reference points and rest positions ("land-marking"),
and touching and holding the iron. The limitation of writing is that these
ideas cannot all be conveyed simultaneously. As with swimming, which can be
described as the integration of kicking, paddling, breathing, and adopting a
good posture, the components of this discussion must be taken together when
performing the task of soldering.
It goes without saying that the techniques to follow should be practiced
while the iron is cold. In addition, a practice iron which is always cold may
be worth having. A dummy iron can be made by thrusting a pencil through a
couple of bottle corks of appropriate size; the pencil should protrude the same
distance as does the hot portion of your iron, and the corks should be of a
size that roughly simulates the handle of your iron. With this tool, you can
take a practice run any time you want to. Even for veterans like myself, an
occasional need arises for a practice shot. For example, when working in a nest
of wiring or when working in a small space, a practice run can lead the way to
taking the best approach, and may spare you an unpleasant surprise.
Surgeons, jewelers, and people working in micro-assembly all know how to
hold their tools and to support their hands to maximize control and stability.
We will take the following lessons from them. (My thanks to Dr. Irene Gilbert
of University of California Medical Center and to Dr. Brian Brown of
Smith-Kettlewell Institute for these lessons in physiology.)
We possess one set of muscles capable of precise manipulation, the thumb and
fingers. The muscles have a large number of nerve fibres dedicated to them, and
a large part of the brain is devoted to controlling them. In Dr. Gilbert's
words, "The area of cortical neurons overseeing the thumb alone is almost
as large as the area over-seeing the entire leg and foot. Therefore, precise
manipulation of instruments can best be done with the thumb and fingers.
Coarse muscle systems which are not designed for fine work, namely muscles
controlling motion of the arm, should be taken out of play. Free motion of the
arm has a profoundly detrimental effect on the precision of finger motion. The
main muscles which operate the fingers are not actually in the fingers, they
are in the forearm. The fingers are controlled through a complicated pulley
system of tendons and ligaments in the wrist. Precise control of the thumb and
fingers cannot be attained through an unstable pulley system.
Much of what is seen as hand and finger tremor is caused by failure to
stabilize the arm and wrist. People who do fine work learn quickly to stabilize
their wrists and forearms on solid objects. Dr. Gilbert remarked, "I once
made a plaster half shell of my forearm from elbow to wrist and mounted it
through a ball and socket onto a base. The shell could pivot and rock, and yet
hold my wrist and forearm steady, leaving my fine hand and finger muscles to
manipulate freely and precisely." At the very least, your elbow should be
braced against your body, and your wrist or hand should be resting comfortably
against some solid object. Bracing your hand against the work piece is often
sufficient; however, books, blocks, or the spool of solder should be used as
Holding the iron like a pencil is usually advocated in discussions on
soldering. With the side of your hand resting on the stabilizing object, the
iron is held between your thumb and first finger, with the middle finger curled
under the handle to provide a supporting cross-bar. I modify this grip by
uncurling the middle finger and placing it along the handle under the index
finger; this arrangement gives me better vertical position information. I hold
the solder between my thumb and middle finger of the other hand, leaving the
first finger free to touch and guide the iron where necessary. To maximize
control of it, the solder should be held about three-quarters of an inch from
In the performance of all tasks involving movement, the sense of joint and
muscle position (kinesthetic sense) is relied upon heavily. When pianists and
typists have reached perfection, they no longer look at the keys. A skill is
really learned when one can say, "I can do it with my eyes closed."
In soldering without visual feedback, much about the position of the iron
can be predicted using the kinesthetic sense, but the limits of this
bio-physical system must be understood. "Can the sense of the position of
your hand ever achieve a resolution of one-tenth of an inch, which is necessary
for soldering integrated circuits?" This question must be answered with
another question, "Where is your starting point with respect to the
target?" The accuracy with which a movement can reliably be made is a
fixed proportion of the distance to be moved. Generally, it is about 5 percent
of the distance to be moved, and so to achieve the accuracy necessary for
soldering integrated circuit pins, the last movement should be from a land-mark
about two inches away. I propose that a few reference points and rest positions
along the way to the target be identified, a procedure I shall call
Note the position of main items associated with the project on which you are
working. While holding the iron in your hand, these items can be located with
the heel of your hand or with a couple of straying fingers. By bringing the
iron over to one of these cross reference points, the distance to the target
can be reduced to at least one-fifth the original distance (from the rest
stand). By staying in contact with these items (using them as rest points to
stabilize your hand), the iron can be very precisely controlled with the thumb
For the next stage, the iron can be used to do some of the land-marking.
There are usually a number of relatively inert items which will not be harmed
by bringing the barrel or the tip of the iron into brief contact with them. The
edge of the chassis, the handle of your vise, or strategically placed C clamp, alligator
clip, or clip-on heat sink are examples worth noting. If you are as lazy as
your Editor, you may use the edge of the circuit board, a nearby terminal
strip, or the body of a Bakelite component for land-marking with the iron
(naughty-naughty). Make sure that the tip of the iron is wiped free of solder
before you do this, or you will spill droplets of solder into the project.
Remember, be gentle with the tip at this time, since it will be vulnerable to
damage without its protective coating of excess solder.
The final land-mark should be chosen so that you have a short hop to the
target. Regarding the choice of this landmark's position, Dr. Gilbert suggests
that the following information on current research be noted:
- Movements made horizontally are more precise than those
- One is more accurate in knowing a movement's direction
than the length of the movement.
During the final reach, the iron becomes your "cane". In this way,
it can indicate to you when it has come to rest on the target. Unlike the
"cane" traveler, the person wielding the soldering iron has control
over the features of his terrain. He can arrange for the target to have unique
features. Some examples of this are listed below:
- If a component is being soldered into a printed circuit
board (PC board), leave the leads long, so that the target is "the
only tree in the forest". These long leads will be easy to find with
the tip of the iron, especially if you remember to cut the excess wire off
components you have previously soldered.
- A wire being soldered to a terminal lug may be arranged so
that its end protrudes beyond the terminal, making this terminal easy to
find with the iron. After it has been soldered, cut off the excess wire.
- When wiring integrated circuits on perforated board
(point-to-point wiring), lay a component lead across its intended IC pin;
cut it off so that it extends conspicuously beyond the center line of the
IC (between the two rows of pins). When approaching this connection with
the soldering iron, reach not for the IC pin but for the point at which
the component lead crosses the center line of the IC. In other words, fish
for the extended wire with the tip of the iron; when you have found it,
follow it over to the pin. After this connection has been soldered, cut
the excess wire off close to the pin and proceed to the next pin. Arrange
the order of your tasks so that the pins are soldered in consecutive
sequence (it is harder to hit the pin if it is between two previously
soldered ones). (You will have more space between pins and have less
trouble with bridging them if you use only one component lead per pin.
Other components going to this pin can be soldered to the lead of the
- When soldering multi-pin components on which the pins are
very long, such as PC-mount potentiometers, and wire-wrap sockets, solder
these pins in sequence, and cut them off near the solder joint as you go.
Touching the Iron
With some jobs, such as soldering components with short leads into a PC
board or removing defective components from a PC board, no convenient system
exists to give the target unique features by which it can be easily found. In
such cases, the iron can be guided into position by a free finger of your other
hand. Believe it or not, the hot iron can be touched.
In touching the iron, two overriding principles must be adhered to: the tip
must be wiped clean, and you must not make any quick, uncontrolled movements.
Any fisherman knows not to make fast jerky movements around his tackle,
otherwise he may impale himself on a hook. The same philosophy should prevail
when handling a hot soldering iron. The more relaxed and even your motions are,
the less chance you have of coming into unexpected firm contact with the barrel
or tip of the iron. If the job is such that you must touch the iron, do so with
smooth, light, brushing motions. (Your Editor considers that fear of such
things is relative. I would much rather solder than light a cigarette, which
scares the Devil out of me.)
When you have hit the target, several indications can be used to affirm that
it is the desired one. At this point you have a "cane" in each hand
the iron is in one hand, and the solder (which awaits your arrival at the
target) serves as a "cane" in the other hand.
Using the iron as your "cane", the contour of the target should
make sense as you gently scan it with the iron.
The solder, which is being held against the connection by your other hand,
will vibrate when the iron touches the connection. At this point, move the
solder over to where you suspect the tip of the iron is resting on the
connection. If it melts, the iron is on target and you were right about its
position. Bring the solder back to a point which is not in direct contact with
the tip of the iron and feed the desired amount of solder to the joint (from
one-eighth to one-half inch depending on the size of the connection and of the
The solder may melt immediately when the iron touches the connection; this
is your indication that the iron and the solder touched the target in the same
place. Often, you will lose the connection with the solder. When this happens,
feel around with the solder until you apply it to the connection which causes
it to melt.
Another indication of hitting the desired target is that the wiring and
components associated with the connection will heat up. A spare finger of the
solder-feeding hand can be used to monitor this condition.
Indications that you have missed the target are:
- Components associated with a different connection may heat
up, indicating that you have found their connection instead of the desired
- The solder will refuse to melt when it is scanned over the
connection. Scanning adjacent connections with the solder will reveal
which one is being mistakenly heated.
- If you suspect that you have gotten on to the wrong
connection, there is a clue which may indicate to you whether or not this
connection has been previously soldered. If small motions of the iron feel
"squeaky", the surfaces against which the iron is in contact are
wet with solder, which probably signifies that the connection has been
soldered before (if the work materials have been previously
"tinned", the iron may be squeaking against individual items
rather than a fully completed solder connection). If small motions of the
iron do not feel "squeaky", the items you have contacted have
never been soldered.
Tools and Accessories
When people refer to the "balance" of instruments, they are
actually referring to the ease and control with which these instruments can be
manipulated. Used in this sense, the term "balance" implies that a
favorable compromise in weight and distribution of mass was made in the design.
In general, the tools of the highest utility are those which are light in
weight, and which present a minimum of inertia.
It follows that smaller tools are easier to control than larger ones,
because characteristics unfavorable to manipulation become less significant.
For many years I used a large fancy jack knife whose handle contained a pair
of pliers. However, for many small jobs (such as stripping wire) it was clumsy
to hold and would frequently topple out of position. Since then, I have come to
prefer very small pen knives with no extraneous gadgets in the handle.
The above principles can be expanded to include all hand tools used in
soldering. Short light-weight tools which can be held near their center of
gravity afford precision control and promote stability when holding them in
With regard to vises and holding clamps, "low-profile" systems are
preferable. Having the work close to the work bench puts you in a comfortable
position and greatly increases the number of objects against which your wrist
can be stabilized.
The cleaning sponges which come with the rest stand of most soldering irons
are of the simplest configuration, flat. While these are better than using your
apron, several passes must be made over them while the iron is being rotated in
your hand. This cools the iron, weakens the power cord, and does not guarantee
that the tip will be wiped free of dangerous droplets of solder.
Tweezers and Heat Sinks
Forceps which can lock or clamp on to wire leads are very useful tools.
These devices can be clamped on to the leads of heat sensitive components in
order to absorb the heat and prevent damage to the components. These forceps
can be used as "handles" by which wire leads are held in place while
My favorite tools of this kind are surgeons' forceps. Shaped like scissors,
they can be used as very small pliers to aid in forming wires around connection
terminals. They have mechanisms allowing them to be locked in to place. Being
made of stainless steel, they cannot accidentally be soldered into the project.
Spring-loaded heat sinks can serve many of the same purposes.
Vises and Holding Devices
A good strong vise is the best tool for rigidly supporting a work piece. A
vise takes on a new measure of convenience when it can be swiveled to orient
the work in a favorable position for soldering.Besides traditional vises,
fixtures specifically designed for holding circuit boards have become very
popular. Many such holders grip one edge of the board between two strips or
blocks. In order for this type to be used, a section along one edge of the
board must be left free of circuit elements. Holders made by Panavise on the
other hand, hold opposing edges of the board between two spring-loaded V-shaped
channels. This arrangement permits the greatest flexibility of board layout.
All board holders have provision to flip the board over, so that work can be
done from either side.
The basic differences between a sighted person soldering and a blind person
soldering can be described in terms of feedback. There is no argument that the blind
person is operating "open loop" (without direct feedback) part of the
time. In reaching from one place to the next and in ascertaining what is
actually happening during the soldering process, the blind person is forced to
use discontinuous bits of information, whereas his sighted counterpart has
information which is continuous. The gaps - the discontinuities in information
can be made less significant. By shortening the reach, a target can be hit
fairly accurately without vision. By attending to alternative or indirect cues,
deductive reasoning can verify facts which are not seen. These principles are
not new, but they have tragically remained unsaid.
Blind people have been soldering throughout this entire century. As for
myself, I was employed as a technician for three years building very complex
electronic equipment. Since then, I have wired the prototypes of my own