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It's current controlled to make clear, stable colloidal silver that's rich in isolated ions and small particles!

Meters and Lasers

Colloidal silver water contains electrically conductive (Ag+) dissolved silver IONS, AND non-conductive colloidal PARTICLES. Ions and particles have completely different properties and need to be addressed separately. Here's a couple of popular optional extras that help you do just that.

You can roughly MEASURE the PPM of the silver ions in your silver water with a TDS or EC Meter, OR you can OBSERVE the particles (colloids) with a Laser.


(For more information about ions and particles theres a lengthy discussion at the bottom of the 'Making CS. FAQ's' page)

NOTE. Beware of cheap, unreliable copies of these quality meters. Genuine HM Digital products carry the HM Digital logo. We buy direct from HM Digital and receive quantity discounts so you save money.

HM Digital 'TDS 3' PPM and Temperature Meter

A TDS (Total Dissolved Solids) meter is an extremely handy addition to your colloidal silver kit. It measures the initial purity of commercial or home distilled water, and provides a useful guide to the final ionic PPM (Parts Per Million) of your colloidal silver. Its also very handy for testing the quality of your mains water, rain water or bore water.

This good quality meter features advanced microprocessor technology.
- Hold Function (saves measurements for convenient reading and recording).
- Auto-off function (shuts off automatically after 10 minutes to conserve batteries).
- The measurement range is from 0-9990 ppm. From 0-999 ppm the resolution is in increments of 1ppm. From 1000 to 9990 ppm, the resolution is in increments of 10ppm indicated by a blinking 'x10' image.
- Temperature gauge.
- Includes a neat carrying case with belt clip.
- Uses just 2 button batteries, not 4 like the similarly priced blue Hanna TDS-1 and it has much bigger, easier to read numbers, and is easier to use than the Hanna meter too.


Note 1. All TDS and PPM meters actually measure conductivity not PPM.

All TDS/ppm meters work by measuring the electrical conductivity of the water. Then they convert that reading to an estimate of the amount of dissolved ions in the water. This estimate is then displayed as PPM (or parts per million). Only the dissolved 'charged' ions in the water are conductive so a meter is only estimating the PPM of the IONS. They cannot detect or measure the PARTICLES (also known as colloids) as these are not actually dissolved and therefore they are non-conductive. In clear colloidal silver it is generally assumed that the IONIC component will constitute 85% to 95% of the TOTAL PPM. The PARTICLE component, even though it is not measurable by the TDS, would be an additional 5 to 15%. (That's assuming you started with pure water with a near zero reading). The Tyndall Effect described at the bottom of this page is the simple indicator of the presence of the particles in the water that the meter cannot detect.

Note 2. All TDS meters think they are measuring salt not colloidal silver! So you have to double what it says on the meter.

All TDS meters are factory calibrated to provide an estimated PPM for the most common dissolved ion; sodium chloride (salt), not colloidal silver. But salt is about twice as conductive as silver ions, so when using a TDS meter to estimate the ionic PPM of COLLOIDAL SILVER the recommended practice is to multiply the reading on the meter by 2 to 2.5 times because it has actually taken at least twice as many silver ions to reach the level of conductivity indicated on the meter. So, for example, if the TDS meter says 6 then your actual ionic silver PPM is probably between 12 to 15 ppm. ALL TDS METERS work as described here! So if anyone tells you you can simply read a colloidal silver strength directly off the dial of a TDS meter they dont know what they are talking about.

Note 3. You DO NOT subtract the original reading.

If you started with pure or near pure water you DO NOT SUBTRACT the original reading from the final reading as some people suggest. If fact it is probably more accurate to ADD the original reading to the final 'doubled' reading. This is because the original reading is ionic salt and will combine with the silver ions to form non detectable silver compound particles. Although these particles are no longer measurable by the meter, the silver is still 'in there' so it should be taken into account, even though the meter can't read it.

Note 4. TDS meters are 'non selective'.

TDS meters (and EC meters such as COM100 below) cannot distingish between silver ions (Ag+) and various other types of common impurities such as dissolved salt. So to use any meter for measuring colloidal silver you must start with pure water that contains no impurities.

By the way... PPM and 'Milligrams per litre' are the same thing. So, for example, 15ppm is the same as 15 milligrams per litre.

You can read more about PPM and TDS meters on our 'Making CS. FAQs' page.

'Com 100' combined EC (Electrical Conductivity), PWT,
TDS/PPM, and Temperature Meter.

Heres a great meter at a fantastic price. It measures total dissolved solids (TDS/PPM) like the meter above, but it also measures EC (electrical conductivity) like a Hanna PWT meter. And it provides a continuous temperature display too. This unit is very simple to use 'straight out of the box' but it provides all the features you need for measuring water purity to a high degree of accuracy.

Electrical conductivity is displayed in microseimens (uS) to 1 decimal point.
1 uS is considered to be equal to 1 PPM of colloidal silver so this is the easiest and most accurate method for home CS makers to determine the PPM of their 'home brew'.
You don't have double the figure on the meter like you do with a TDS/PPM meter. (I highly recommend you read Notes 1,2, 3 and 4 in the TDS meter section above).

- Measures in Microseimens (uS), Milliseimens (mS), Parts per million (ppm) in 2 calibrations, and Parts per thousand (ppt).
- Measurement Range is 0-9990 µS or 0-5000 ppm in 0.5 (NaCl) mode. (This is way beyond the Hanna PWT that only measures to 199 uS which is too low for most tap water).
- Features EC mode with readout in microseimens and milliseimens.
-TDS mode is in 2 calibrations: ppm/0.5 (NaCl) and ppm/0.7 (442) .
- Automatic Temperature Compensation using three temperature coefficients.
- Fully Waterproof (It's submersible).
- Auto-off function (Saves batteries).
- Data-hold function and low-battery indicator.
- Large and easy-to-read LCD screen includes simultaneous temperature reading.
- Platinum electrodes.
- Factory Calibrated, but the meter can be recalibrated with digital calibration using the push buttons, rather than a screwdriver.
- Includes a cap, batteries and lanyard.
- Dimensions: 18.5 x 3.4 x 3.4 cm.


1: Meters can only measure the dissolved (ionic) silver. The saturation point of dissolved silver in pure water is usually about 20 to 30 ppm. (It varies with water quality and temperature). Above this saturation point the ionic silver combines to form solid particles that are not measurable by the meter. This means that no matter how long you continue to run the generator, the meter will usually not indicate an ionic silver ppm higher than about 20 to 30 ppm. So if the generator is running, but the meter reading stops rising, it means the silver water has reached its saturation point. From that point onwards, all the meter is telling you is that the actual ppm is ‘somewhere above’ the figure being displayed on the meter, it does not mean that the generator has stopped dissolving silver into the water or that the total ppm has stopped rising. (The total ppm is the sum of the dissolved silver ppm and the silver particles ppm.). Regardless of what the meter says, any generator is always raising the total ppm of the colloidal silver for as long as power is supplied to the electrodes. Furthermore, the ppm reading on the meter can even appear to go DOWN as you dissolve more and more silver into the water. This is because the silver that had previously been dissolved now begins to combine with the ever increasing number of particles in the batch.

(Producing CS above the saturation point can be useful but is problematic. The silver water may be slightly coloured and it will not store as well, thats why the auto-shutoff mode of the Silver Well is automatically set to switch off at about 12 ppm, comfortably below the saturation point. This is safe and effective for human consumption and it stores well. In manual mode you can run the Silver Well to produce colloidal silver with a total ppm as high as you like. This is ideal for topical applications, gels, and diluting in larger water storages. (Most 'bought' colloidal silver is bottled at well below 15 ppm. This affords it a long shelf life but in my opinion it is often too weak to be very effective). )

2: For two reasons all meters are completely useless for determining the ppm of silver in impure water. Firstly, in impure water the silver ions immediately combine with other ions and impurities to form particles that are not detectable by the meter. And secondly, the meter can't determine between different types of ions so it will simply measure all the ions in the water, silver and otherwise. So if you wish to use a meter to measure your home-made colloidal silver you must start with pure water (below about 2 ppm).


Many people think that a PPM meter gives a definitive reading of the purity of water. This is not true. A ppm meter can only detect those dissolved impurities that raise the electrical conductivity of the water. So a meter can only determine the ppm of the dissolved NON-ORGANIC impurities (e.g. dissolved salts) because only these impurities raise the conductivity. It cannot detect the dissolved ORGANIC impurities* that may also be in the water (e.g. sugar or rotted leaf litter). Nor can a ppm meter detect the microscopic solid particles that may be in the water (i.e. the grit). So a cup of distilled water that contains a tablespoon of sugar and finely powdered glass may display a ppm reading of near zero even though its obviously not pure.

So, when using a ppm meter to measure water purity, you have to know if the dissolved organic impurities and the fine particles have been removed along with the salts. The only way to remove all these impurities is with a high quality reverse osmosis/deionisation system or with careful steam distillation.

The shortcomings of meters mentioned here should especially be considered when measuring the purity of rain water. Although the rain water may initially be pure, it can become significantly contaminated by organic impurities in the gutters and the tank. Although these impurities are not detectable by the meter they can have quite a detrimental effect on colloidal silver production.

(* One qualification to the comment above about the 'non conductivity' of organic impurities concerns the presence of acid. Any acid raises the electrical conductivity of water and can induce a completely meaningless reading on a ppm meter. While organic impurities usually do not register on a ppm meter, a few drops of, say, acidic lemon juice in a glass of water will produce readings in the 100's.)


For viewing the Tyndal Effect. What's the Tyndall Effect? The easy explanation is that its light shining off microscopic colloidal particles in a liquid. It's a way to see the normally invisible colloidal portion of your clear silver water. (These particles are not detectable by a TDS meter so this is the only way to be sure they are really IN there.) See the photo below of the red laser line reflecting off the particles in the glass of clear colloidal silver.

You don't normally need this instrument to make CS, but some people like to see the results of experimenting with different processing times and other variables.

An example of the Tyndall Effect

The picture at left of a glass of crystal clear Silver Well CS was taken in daylight, not in the dark. The red laser line shows a dense, but not sparkly 'Tyndall effect' proving the presence of abundant very small particles.(Sparkles would indicate large particles.)

The Tyndall Effect (TE) is a visual indication of the presence of silver particles in the colloidal silver. Under a bright focused beam of light the normally invisible silver particles in the colloidal silver become visible as tiny points of light suspended in the water - even though in ordinary daylight the CS appears perfectly clear. With practice the Tyndall Effect is a visual guide to the type of CS you are making. (Whether you have numerous very small particles, mixed fine and coarse (sparkling) particles, or mainly coarse particles). For example, clear CS with a dense satin red line indicates abundant fine particles. (i.e. really nice CS, as per the Silver Well sample at left.)

Note: The Tyndall Effect is the simplest indicator of the presence of tiny silver particles but it does not reveal ions. TDS and PWT meters measure the ions but conversely they cannot detect the particles.

You can read more about the Tyndall Effect on our
'Making CS. FAQs' page.

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