Gold Testing with a Tri-Electronic Tester

Gold Testing with a Tri-Electronic Tester

Many pieces of antique gold jewellery (particularly from the Georgian era or pieces which are handcrafted) are unmarked and therefore gold testing is necessary. This article is a practical guide to using an electronic gold tester made by TRI electronics (I personally have the GXL-18 model.).  

This is my decimation of the information in the TRI Electronics user manual which I hope makes a good quick reference for those interested.  HOWEVER – PLEASE ALWAYS REFER TO THE MANUFACTURERS INSTRUCTIONS FOR THE FINAL SAY ON HOW TO USE THESE TESTERS. 



The procedure for testing can be shortened to the following easy to remember four words:


For more details, see below: 

1) Load the polyethylene gel tube in accordance with the manufacturers instructions.

2) Connect the following:

a) The black wire to the sensor’s plug outlet.

b) The black and red wire connector to the display unit.

c) The red wire to the testing plate.

3) Turn the unit ON. The unit should now read ‘G-XL-18 READY TO TEST…’

4) Selecting a point to test: 

a) Make sure the point to test is close to BUT NEVER TOUCHING the alligator clip.

b) Do not allow the gel to touch the alligator clip as this will corrode it.

c) Thoroughly clean the testing point with the eraser.

5) The First Part of the Test

  1. Place a tissue, paper towel or rag under the tip of the sensor.
  2. Hold the sensor in a vertical position with the nozzle down.
  3. Twist the Rotary Cap counter clockwise, one click at a time, until a drop of gel appears.
  4. Wipe this first drop of gel away.
  5. Turn again (usually one or two clicks) until more gel appears.
  6. Touch the sensor to the selected area of the test object.

6) Select a gold colour button. 

Depending on the visible colour of the metal you are testing, select one of the following buttons on the unit (see manual for diagram of button locations):





7) Keep the sensor in a vertical position for about 5 seconds. This is is when the gold value is calibrated.

8) The karat value and European Standard are displayed on the instrument. (Tip: Write this down with a pen and paper you keep to hand, along with your reference for the item).

9) Turn off the instrument.


1) Electronic tests are not infallible.  If you achieve a result which is outside of expectations then retest in a different location after cleaning your equipment and your item and use new gel. Keep testing until you get a consistent result. Always make a note for the customer if you are selling gold items tested with an electronic tester explain that the test is not infallible and should be seen as a guide only. 

2) Be careful with fine chains. Very fine chains  can be crushed by the dispenser. Avoid pressure with fine gold chains whilst keeping gel contact. It’s recommended to get the results of two or three tests.

3) Be aware of air bubbles. Sometimes air bubbles with give a high or low reading. Always retest and apply common sense to the results of your readings.

4) Clean Tip. A clean tip is essential for an accurate reading.

a) If you are not using the gold tester more than once a week it is advised that you remove the gel tube from the sensor and store it to keep the gel from drying out.

b) Before replacing the gel, whether with a new tube or with one previously removed, clean thoroughly with SC-10 Cleaner Kit. 

c) If the tester has not been used for over a week, clean the tip with the plastic cleaner provided by inserting the tip into the nozzle of the sensor.

d) If gel drops are not dispensed by rotating the twist cap, clean the sensor with the SC-10 Cleaner Kit. 

5) Solder areas and heavy castings with unevenly dispersed metal can give false readings. Always retest in different areas of the piece.

6) Italian Gold may be waxed and can give a false reading. If you suspect the metal may be waxed, clean the testing area with heavy erasing or with nitric acid (only a drop is required).

7) Skin oils can give a false reading. In heavily worn pieces clean the testing area first with the eraser or with non-acetone nail polish remover.

8) Plated Gold. Usually a tiny scratch or a pin prick will allow gel penetration to the base material on plated pieces. If this is not sufficient, two or three tests are recommended with a thorough eraser cleaning in between. If the item is gold plated, the karatage will decrease with each testing. A solid gold piece will not decrease with each test.

9) Dispose of the drop of gel following each test. 

10) Use every other gel drop for best results. 


12) When removing the cable from the sensor, do not pull the wire! Pull the plug itself to avoid damage. 

13) Testing objects larger than the Alligator Clip. In this instance, unhook the red wire from the testing plate and proceed with the test as per instructions but with the tip of the red wire touching the object.

14) Do not retest the same spot without eraser cleaning.

15) Refer to the manual for full care and maintenance of the tester and follow their recommendations.  


1) Problem: Brown spot on test surfaces

Solution: Rub the spot with eraser

2) Problem: Display unit reads “NOT GOLD”

Solution: Check the wire contacts and the connections

3) Problem: Display has no reading

Solution: Check batteries or switch to converter or change the wire set.

4) Problem: Inaccurate or different readings

Solution: Keep gel away from alligator clip

5) Problem: Gel does not come out

Solution: Clean sensor nozzle and check gel tube and replace if empty.

6) Problem: Sensor’s rotary cap is hard to turn or is tight.

Solution: Check gel tube and replace if empty.

7) Problem: Changed or reduced karat value on the display from previously.

Solution: Check gel tube and replace if empty.

Copyright © 2017 by Pippa Gaubert Bear and Elder & Bloom. Unauthorized use and/or duplication of this material without express and written permission from this website’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Pippa Bear and Elder & Bloom with appropriate and specific direction to the original content.

Understanding gold

The use of gold in jewelry in every era is so completely ubiquitous that it is easy to forget that gold itself is also subject to the ebb and flow of fashion.  Each era, with it’s particular technical abilities, sensibilities and levels of wealth has a different relationship with gold in jewelry.  Gold, the most malleable of all metals, can be utilized by the jeweler in a variety of ways: chasing, repoussé, filigree, cannetille, soldering, granulation, piercing and casting.  Indeed, gold’s relative level of scarcity in any given era has been the driving force between many creative breakthroughs in jewelry design.  Many of the aforementioned techniques are designed to increase the appearance of volume in gold and to maximize its impact.

There is really a great deal to say about gold so I would like to focus as much as possible on the basic and practical aspects of understanding and evaluating gold in an antique jewelry piece.

A diamond-set locket

A Diamond-set gold locket
Sale 8127
16 January 2013
London, South Kensington

Understanding gold basics


Up until the mid 20th century, gold has always been measured in karats (also written kt or k). This is not to be confused with ‘carat’ which measures gem weight. However, in Britain and some other countries ‘karat’ is spelled ‘carat’ just like gem weight.  (Confusing I know!)

The ‘fineness’ of gold refers to the amount of actual gold present.

One karat is 1/24 of the total purity of the gold.


24 k gold is 99.99% pure gold.

18 k gold is 75 % gold and 25 % another metal

14 k gold is 58.3% gold and the rest is another metal

10 k gold is 41. 7% gold and the rest is another metal


Another, possibly easier way, to say this would be to say:

24 k is 24 parts gold

18 k gold is 18 parts gold, 6 parts another metal

14k gold is 14 parts gold, 10 parts another metal

10 k gold is 10 parts gold, 14 parts another metal


Non-karat gold

In the USA the following applies: lower than 10 k gold is not allowed to be called ‘karat gold’

In the UK the following applies: lower than 9k is not allowed to be called  ‘karat gold’

In Germany the following applies: lower than 8k gold is not allowed to be called ‘karat gold’

Below these amounts, gold is not considered to be karat gold and is normally referred to as ‘low-karat gold’ or ‘a gold alloy’ or ‘coin gold’.

Gold colors

There is only one color that actual 24k gold can be.

In order to make it all the different colors, gold is alloyed with different metals in different quantities to achieve the variety of results we are familiar with.

Normally, gold is referred to as being one of the following:

Yellow gold – this is when it is alloyed with gold, copper, silver and zinc


Gold ‘Manchette’ or cuff bracelet, c. 1860, England
V&A Museum

Rose gold – this is when it is alloyed with copper and silver, with proportionally more copper than silver.

Antique Rose Gold Bracelet.

Rose Gold Bracelet, c.1900

White gold – this is when it is alloyed with nickel or palladium, copper and zinc


Art Deco diamond, white gold and platinum bracelet
Sale 3517
Paris Jewels
5 December 2012

Green gold – this is when it is alloyed with gold, copper and silver, with proportionally more silver


Purity marks

Gold has been purity marked  since the Middle Ages and this is a very useful way of understanding the karat of gold, as well as helping to give an indicator of age and origin. The purity mark is one of the very first things to look for when evaluating a piece of jewelry.  A purity mark indicates the percentage of precious metal in the piece.

Generally, countries which have used non-metric systems such as the USA and Great Britain, will have a purity mark for gold written as follows:

24 k, 18 k, 14 k, 10 k, 9 k, 8 k (or in the case of the UK – 24 ct, 18 ct etc)

Countries which have traditionally used the metric systems, such as continental European countries, will have purity marks for gold written in the following way:

1000/1000 is pure gold and will be marked as ‘1000’, 750/1000 is 18k gold and will be marked as ‘750’, 583/1000 is 14 k gold and will be marked as ‘583’, 333/1000 is 8kt gold and will be marked as ‘333’

In addition, many countries use a pictorial mark to indicate purity so it is best to refer to a library (see resources at the bottom).

Responsibility marks

The  ‘responsibility mark’ is also known as the ‘maker’s mark’ as well as the ‘manufacturer’s mark’. This doesn’t necessarily name the maker but rather who is responsible for the stated purity of the metal. In countries with a long  tradition of mandatory maker’s marks, these marks were always unique to each maker.  They usually had the initials of the maker with a pictorial image. Sometimes, the maker’s marks had to be a specific shape, for example the lozenge shape in France which became mandatory from 1797 onwards. In the USA these marks were made mandatory in 1961. On English, and later on USA, pieces you frequently see an ampersand (for example S&P). Maker’s marks were normally struck by the manufacturer and registered at the assay office.


In the UK, Dateletters have been used since 1478 and gold and silver had to be marked at the “hall’ (hence the word “hallmark). A new letter of the alphabet was used every 25 years (some letters were skipped). A different letter font and/or design of the letter border was used every cycle to differentiate.  This gives jewelry historians an excellent way to find the age of a piece.  Very delicate pieces, however, did not have dateletters as there was no room to put them

Other Marks

Town Marks

Specific towns took on their own marks.  For example, a famous one is Birmingham’s anchor.

Tally marks

Sometimes found on UK and USA items.

Duty marks / Import and export marks

Indicated taxes paid or if exempt

Retailer marks

Usually just large stores, ie Tiffany’s

Patent and inventory marks

Usually long numbers, useful in dating. Firms like Cartier use.

Designer marks

Used quite frequently from the Art Nouveau era onwards

Gold purity according to era and country

24 k gold is very soft and generally considered too easily damaged to create jewelry from. In past eras, the people who could afford gold did not do household chores so their jewelry didn’t need to be hard wearing.   As gold came to be worn more and more by regular people, alloys were created for jewelry wear to give strength and durability. Generally speaking, gold from the Georgian era is much more likely to be higher karat than later eras. The Victorians began to cater to the tastes of people who weren’t royalty by creating more practical gold alloys.

As you can see below, gold purity marks can give us a lot of information regarding possible age of the jewelry and also country of origin.

UK and Ireland

Up to 1854, the legal standards for gold were 18ct and 22 ct.  In 1854, 15ct, 12ct and 9 ct were introduced.  In 1932, the 14ct mark was introduced, and the 12ct and 15 ct marks were eliminated.


Prior to the year 1906, most jewelry made in the USA was without any kind of mark.  After this, gold purity marks can be identified as being American by the use of ‘k’ (as opposed to ‘ct’ from the UK).


Before 1884, German gold purity marks was expressed in “Löthig”.  Pure gold was 16 löthig.  So, for example, if you see a piece with ’13’ marked on it, it might well be expressing 13 löthig, which would indicate 812.5/1000.

From 1884 to the current day, German gold purity marks could be expressed in thousands (such as 585 for 14 karat gold) or expressed as a karat like the USA (for example 14k).  They could also have both marks on one piece.


From1838 an eagle’s head has been used to indicate a gold purity of at least 18 karat.

In France, gold jewelry must have at least 18 karat unless it is for export.  Items for export have pictorial marks representing 9 k or 14 k.

Weight of gold as a indication of value

The value of a piece of jewelry is not only indicated by the purity of the gold, but also by the weight of that gold.  It is best to weigh jewelry with a specifically designed sensitive gram scale. In order to calculate the value of the gold itself, if you were simply to look at scrap value, there are various sites online where you can find out the daily price by putting in the weight and the karat of the gold.

Testing gold

Sometimes, it will be necessary to test a piece of jewelry for gold content.  This can be because the hallmark was worn away, because there is no hallmark or because you don’t entirely trust the hallmark.

Gold is not magnetic, so a quick way to eliminate non-gold is to test with a magnet.

There are several different ways of testing gold and metals.  One of these is the acid scratch test.  I will write a separate post at a later date all about testing metals as there is quite a lot to it.

Gold substitutes and look a likes

These include, but are not limited to: pinchbeck, ‘tombak’, ‘schaumgold’, brass, bronze, copper alloy, gold fill, gold plate, painting gold etc etc (I will go into all of these in more detail in the future).

Sources / further reading (be sure to have a look at the sources in the drop down menu also):