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[Source] Deionized water

Every 6 months when I have to do the semi annual service on my Laser
Star, the shipping cost alone on a gallon of the required “deionized
water” is more than the water itself which is itself quite pricy.

Information I have looked up online is a bit confusing and the term
"deionized" seems to mean different things to different folks. Does
anyone have a more affordable source, or suggestions on producing my

Thanks. Jim Newton

Find a well stocked aquarium hobby supply store near you and go talk
to them. I know one of the large aquarium shops in Denver sells DI
or RO water by the gallon for marine aquarium setups. Hey! Don’t
laugh. It’s somewhere to look. LOL


Hi Jim,

Try your local university’s physics department. Back when I was
closer to such things, the local department had their own still, and
made it up as needed. (not really a still, but that was what they
called it.) Used heavily in cleanroom work, or chip production, so
the engineering department may have a source too.

For whatever that was worth,

Try your local university's physics department. Back when I was
closer to such things, the local department had their own still,
and made it up as needed. (not really a still, but that was what
they called it.) Used heavily in cleanroom work, or chip
production, so the engineering department may have a source too. 

That is distilled water not de-ionized although it would work.
Either one can be typically purchased at a local drug store, and
most grocery stores.

James Binnion
James Binnion Metal Arts

When I was doing plumbing design for a company that had a contract
with Motorola we did an ultrapure deionized water plant for the
entire facility to do away with the UPDIH2O old plant. The new plant
was to have a capacity of over a half million gallons a day. We
started with a reverse osmosis units, then carbon filter, 1 micron
filters, cation bed filters, anion bed filters, mixed bed filters,
ultraviolet fliters,.5 micron filters, then out to the production
mods where it was polished with another set of mixed beds and uv
filters before it ever came in touch with a wafer. Ultrapure
deionized water is not available just anywhere, maybe deionized
water but it had a very bed habit of growing slime bacteria for some

A convenient source of distilled (better than deionised?) water is
the by-product of dehumidifiers. I have a small one in my cellar
that generates about 5 ltrs in a day or so. My wife uses a fraction
of it in her steam iron, but most is dumped.

Regards, Gary Wooding

Hi Jim,

No, really. It was DI water. Something in her lab drank it by the
gallon. They had to run a pipe from the building supply. Another
something down in the clean room also seemed to be quite fond of it
as well. Don’t exactly remember why.


That is distilled water not de-ionized although it would work. 

LaserStar is adamant in their training and literature that distilled
water is not an acceptable substitute for deionized water. They
insist that to insure that the quality of the deionized water is up
to standards that you only buy it from them. I am skeptical, but have
not used anything else because the machine is very expensive and
having it down for repairs would be costly and disruptive.

What do other manufacturers of laser welders recommend?

Stephen Walker
WalkerMetalsmiths. com
Andover, NY

I believe what you need to know is what resistance of the water is
required. Contaminants in water render it conductive, the more
contaminants the lower the resistance. Ultra pure deionized water
can reach 18 megohms/cc, contaminants on the order of a 0.1 ppm can
drop that to 5 megohm/cc.

The measurement may be quoted as conductivity described here

Once you know the spec for the laser you can possibly get it

No, really. It was DI water. 

It would only be DI water if it was run through one or more
de-ionization columns after it was distilled. Otherwise it is just
distilled water.

James Binnion Metal Arts

What do other manufacturers of laser welders recommend? 

Note that it’s possible that differences in materials or engineering
could alter the needs of a machine versus other brands or types. But
the folks at BD tell me that my old beast of a laser is just fine
with distilled water.

Note that distilled means no minerals, salts, etc., but it could have
traces of anything that itself could be boiled off and condensed,
such as organic solvents. But if the initial water used is free of
such contaminants, as is likely the case with most commercially sold
distilled water, then the differences between DI and distilled may be
little, especially after the DI sits in it’s container for more than
a short while.


What do other manufacturers of laser welders recommend? I was told
that I should go ahead and use distilled water, that the unit I have
will deionize the water itself. No problems yet. Mark

What do other manufacturers of laser welders recommend? 

The flash lamp pulses light, the chamber reflects the light onto the
YAG rod to produce the laser beam. This system is under water to
cool the flash lamp and there are two schools of thought about
de-ionized water depending on the composition of the reflective
chamber. If you have a 24k gold plated chamber, it is very important
to have de-ionized water. The electricity that is supposed to go
through the flash lamp will arc through the water and the gold
plating causing damage to the plating. This will decrease your
laser’s power. This is why it is important to change your water at
the manufacturer’s recommended schedule. The Rofin laser welders do
have a water filter that de-ionizes the water so you can
usedistilled water, but still need to change the water and filter
every year or two.

If you have a ceramic chamber, it is less important to have
de-ionized water. Electricity can still arc through the water, but
it rarely damages the chamber. Few manufacturers use the ceramic
chamber due to how much less efficient the ceramic chamber is verses
the gold chamber. This lack of efficiency produces much more heat
and needs larger water-cooling systems (10 gallon versus 2 gallon).

John Vandergriff II
Laser Training Specialist

There is a difference between deionized water, and distilled water.
The distilled will actually be more pure. Especially if you can find
a source of double distillation. When water is deionized it is done
with resins, that might not be fully eliminated in the final step.
Distillation is done via boiling, capturing the steam and letting it
return to a liquid state leaving all impurities behind. If i were to
go for the purer of the two, I would go for distilled. Or is it that
the residual resins are useful for the lazer welder?

Just my thoughts.
Aggie recouping from process to stop pain, that made more pain!

Hopefully the below will be of interest, it has been
derived from various sources. In summary, my way of thinking about
this is distilled is less pure than demineralised which is less pure
than deionised. Where manufacturers specify a particular water grade
it is because they do not want any residual minerals or organics in
the water so I would always follow their recommendations.

Distilled, demineralised and deionised water and measuring of the

It is quite difficult to find clear definitions and standards for
distilled, demineralised and deionised water. Probably the easiest
way to familiarise in the topic of producing (ultra) pure water is
to start with the oldest and best-know method: distilling.

Distilled water is water that has been boiled in an apparatus called
a “still” and then recondensed in a cooling unit (“condenser”) to
return the water to the liquid state. Distilling is used to purify
water. Dissolved contaminants like salts are left behind in the
boiling pot as the water vapour rises away. It might not work if the
contaminants are volatile so that they also boil and recondense,
such as having some dissolved alcohol.

Very elegant stills can selectively condense (liquefy) water from
other volatile substances, but most distillation processes allow
carry-over of at least some volatile substances, and a very little
of the non-volatile material that was carried into the water vapour
stream as bubbles burst at the surface of the boiling water.

Maximum purity (this is discussed towards the end of this post) from
such stills is usually 1.0 MWcm; and since there is no protection
from carbon dioxide (CO2) dissolving into the distillate the pH is
generally 4.5-5.0. Additionally, you have to be careful not to
re-contaminate the water after distilling it.

Demineralisation - this is generally any process used to remove
minerals from water, however, commonly the term is restricted to ion
exchange processes.

Deionisation - this is a process which utilises special-manufactured
ion-exchange resins to remove ionised salts from water. This can
theoretically remove 100 % of the salts dissolved in water.
Deionisation typically does not remove organics, virus or bacteria
except through “accidental” trapping in the resin and specially made
strong base anion resins which will remove gram-negative bacteria.

Deionisation entails removal of electrically charged (ionised)
dissolved substances by binding them to positively or negatively
charged sites on a resin as the water passes through a column packed
with this resin. This process is called ion exchange can be used in
different ways to produce deionised water of various qualities.

Deionised water can also be produced with reverse osmosis plants.
Reverse osmosis is capable of rejecting bacteria, salts, sugars,
proteins, particles, dyes, and other constituents that have a
molecular weight of greater than 150-250 Daltons.

Ultra purer water - this is highly-treated water of high resistivity
and no organics; usually used in the semiconductor and
pharmaceutical industries.

Measuring Water Purity

Water purity may be measured in various ways. You can attempt to
determine the weight of all of the dissolved material (“solute”);
this is most easily done for dissolved solids, as opposed to
dissolved liquids or gases. In addition to actually weighing the
impurities, one can estimate their level by the degree to which they
increase the boiling point or lower the freezing point of water. The
refractive index (a measure of how transparent materials bend light
waves) is also affected by solutes in water. Alternately, water
purity can be quickly estimated on the basis of electrical
conductivity or resistance - very pure water conducts electricity
poorly, so its resistance is high.

Quality Ultra Pure Water Pure Water Purified Water

Typical Resistivity 10-18 MOhm. cm 1-10 MOhm. cm 1-0.02 MOhm. cm

Conductivity 0.1-0.0555 microS/cm 1.0-0.1 microS/cm 1.0-50 microS/cm


Pure water by definition is slightly acidic and distilled water will
test out around pH 5.8. The reason is that distilled water dissolves
carbon dioxide from the air. It dissolves carbon dioxide until it is
in dynamic equilibrium with the atmosphere. That means that the
amount being dissolved balances the amount coming out of solution.
The total amount in the water is determined by the concentration in
the atmosphere. The dissolved carbon dioxide reacts with the water
and finally forms carbonic acid.

2 H2O + CO2 --> H2O + H2CO3 (carbonic acid)

Newly produced distilled water has a pH value of approximately 7,
but is affected by the presence of carbon dioxide it will reach a
slightly acidic pH-value within a couple of hours.

Additional, it is important to mention that the pH of ultra-pure
water is difficult to measure. Not only does high-purity water
rapidly pick up contaminants - such as carbon dioxide (CO2) - that
affect its pH, but it also has a low conductivity that can affect
the accuracy of pH meters. For instance, absorption of just a few
ppm of CO2 can cause the pH of ultra pure water to drop to 4.5,
although the water is still of essentially high quality.

F. N. Kemmer; The Nalco water handbook; 2. Edition; 1988
Degremont; Water treatment handbook; sixth edition; 1991
Osmonics Pure Water Handbook; 2. Edition; 1997

Charles Allenden

Although their lasers come with deionized water, Rofin specifically
states that steam distilled water is OK to use in their lasers.
Their filtration system deionizes the water.