Chlorine test

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Intro

The laser can successfully cut many materials that it shouldn't. In particular, materials containing chlorine (like PVC) release vapor that will corrode the laser's parts and also your lungs.

A simple test can determine if a material contains chlorine, though it won't guarantee that the material is safe to use.

Procedure

Do this outdoors or under the welding hood when possible.

You will need:

• Thick copper wire (A tube of these is in the Trotec PC drawer)
• Pliers
• Propane torch (Usually found in the welding area)
• A small sample of your material

1. Use a pair of pliers to hold the end of the wire in the flame for a few seconds

2. Stab the still-hot wire into a sample of your test material - try to get a decent amount of it melted on there

3. Put the wire back in the flame

• If the flame turns emerald green, chlorine is present in the material and it must not be used in the laser cutter.
• If the flame remains blue or orange your sample does not have (much) chlorine. This does NOT automatically mean that it is safe in the laser.

With any new material, proceed with caution and watch carefully for fire, thick smoke, or sputtering.

Known Materials

Acceptable:

• Acrylic plastic, clear or colored
• Wood & wood veneers
• MDF
• Cardboard
• Leather
• Fibreglass cloth (no resin)
• Glass (etching only)

Unacceptable:

• PVC plastic. PVC = "PolyVinyl Chloride". The "chloride" means it has chlorine.
• Sintra
• Composites (fibreglass, carbon fibre)
• (Incomplete List)

Trivia

The Beilstein Test: Screening Organic and Polymeric Materials for the Presence of Chlorine, with Examples of Products Tested

http://www.cci-icc.gc.ca/publications/notes/17-1-eng.aspx

http://www.cci-icc.gc.ca/publications/notes/17-1_e.pdf

Chlorinated organic materials are generally considered unsuitable for long-term conservation and museum applications due to their potential harm to objects. These materials may degrade and produce acidic gases, or additives such as plasticizers may migrate to objects. These products can be analyzed in detail in the laboratory, but conservators may use a simple test — the Beilstein Test — to screen their own materials for the presence of chlorine without having to submit samples for laboratory analysis.

The test is based on the reaction of chlorine with copper compounds at the high temperatures found in burner flames. These conditions produce excited, green-coloured copper atoms or ions that cause the normally colourless (or very slightly blue) flame to flare brilliant green (or sometimes blue-green).

The Beilstein Test has been used for many decades to analyze organic and polymeric materials (Shriner et a1. 1964; Vogel 1966). A very similar test is now used by refrigeration technicians to detect and localize leaks of freon-type refrigerants (i.e., chlorinated and fluorinated hydrocarbons). This test has also been recommended for detecting PVC coin storage products (Sharpless 1980).

The Beilstein Test is quite sensitive and requires a very small sample. There are, however, several possible sources of error. Residues from fingerprints can give weak false positive results. Chlorinated inorganic materials (i.e., pigments, fillers) can also give a false positive result, but these are usually not present so they rarely interfere with the test. The major difficulty encountered is that the sample may volatilize too rapidly, especially if it is a solvent. These volatiles are lost so quickly that they do not have time to react with the copper wire. To avoid this problem, the fourth method described above — introducing the fumes at the air intake for the flame — is recommended.

The test is suitable for screening a wide variety of products including plastic films and sheets, adhesives, rubbers, coatings, solvents, and fabricated items. Common materials that give positive results include poly(vinyl chloride), poly(vinylidene chloride), chlorinated rubbers, chlorinated epoxies, chlorinated solvents, and any compositions containing these materials.

The Beilstein Test has been used to examine a variety of materials at the Analytical Research Services laboratory at CCI. The presence or absence of chlorinated organics was confirmed by infrared spectroscopy or by radio-isotope excited X-ray energy spectrometry. The results are presented in the tables below.