⛽ Color of petroleum products (ASTM scale)
In short
Visual determination of the colour of petroleum products — lubricating oils, heating fuels, diesel fuels and petroleum waxes — by comparing the sample with glass colour standards in a colorimeter under an artificial daylight source. The test is performed according to PN-ISO 2049:2010 (Polish version; adopts ISO 2049:1996 [IDT]); Scale: glass colour standards up to 8.0; darker samples — after dilution with kerosine (15 + 85) or the result “D8” (6.1, clause 8). The procedure comprises 6 steps; it is used for: Lubricating oils, heating fuels, diesel fuels and petroleum waxes, including petrolatum (clause 1, 6.2), Only products without artificial dyes (clause 1), Manufacturing control — colour may indicate the degree of refinement or contamination with another product (ASTM D1500).
At a glance
- Standard: PN-ISO 2049:2010 (Polish version; adopts ISO 2049:1996 [IDT])
- Category: Petrochemistry
- Procedure steps: 6
- Scale: glass colour standards up to 8.0; darker samples — after dilution with kerosine (15 + 85) or the result “D8” (6.1, clause 8)
- Reporting: number of the standard, e.g. “7.5”; intermediate colour — letter “L” and the darker standard, e.g. “L7.5”; after dilution the suffix “Dil” (clause 8)
- Sample container: clear colourless glass; referee — the jar in Figure 1; routine — a cloud and pour point jar: internal diameter 30–32.4 mm, height 115–125 mm, wall up to 1.6 mm; filled to at least 50 mm (5.2, 6.1)
Overview
STATUS (as of 30.10.2026). PN-ISO 2049:2010 — Polish version, published 27.07.2010, implements ISO 2049:1996 [IDT]; it replaced PN-C-04034:1980. The PKN catalogue card has no withdrawal note — the standard is current. ISO 2049:1996 (second edition, replaced ISO 2049:1972) — last reviewed and confirmed by ISO in 2025.
SCOPE (clause 1). Visual determination of the colour of a variety of petroleum products, such as lubricating oils, heating fuels, diesel fuels and petroleum waxes; limited to products that do not contain artificial dyes.
PRINCIPLE AND RESULT (clauses 3, 8). The sample is viewed under an artificial daylight source and compared with glass colour standards; the number of the matching standard, or of the one closest to it on the darker side, is recorded, e.g. “7.5 colour”. When the colour is intermediate between two standards, the number of the darker standard preceded by the letter “L” is reported, e.g. “L7.5”. The colour of a sample is never reported as darker than a given standard — except for samples darker than 8, recorded as “D8”. A sample darker than 8.0 may be diluted: 15 volumes of sample in 85 volumes of kerosine; the result for the mixture is followed by “Dil”, e.g. “L7.5 Dil”.
PRECISION (clause 9). With referee sample containers: repeatability — the difference between successive results of the same operator exceeds 0.5 of a colour number in only one case in 20; reproducibility — the difference between results of two laboratories exceeds 1 colour number in only one case in 20.
WHAT WE DO NOT GIVE HERE. The publicly available text of the standard covers clauses 1–10 and the normative Annex A (colorimeter, light source, filter); outside it are Tables A.1 and A.2 with the characteristics of the filter and the colour standards — we do not give their values. The American method ASTM D1500 on the same subject states that colour determination is used mainly for manufacturing control: colour may indicate the degree of refinement, and a result outside the known range for a product may indicate contamination with another product, but colour is not always a reliable guide to quality.
Method principle
A test portion in a clear colourless glass container is viewed in a colorimeter under an artificial daylight source and compared with glass colour standards; containers filled with water stand in the standards compartments, and the whole is covered with a cover that is dull black inside, excluding exterior light. The matching standard, or the one closest to it on the darker side, is recorded (clauses 3, 7).
Applications
- Lubricating oils, heating fuels, diesel fuels and petroleum waxes, including petrolatum (clause 1, 6.2)
- Only products without artificial dyes (clause 1)
- Manufacturing control — colour may indicate the degree of refinement or contamination with another product (ASTM D1500)
Key parameters
| Parameter | Value |
|---|---|
| Scale | glass colour standards up to 8.0; darker samples — after dilution with kerosine (15 + 85) or the result “D8” (6.1, clause 8) |
| Reporting | number of the standard, e.g. “7.5”; intermediate colour — letter “L” and the darker standard, e.g. “L7.5”; after dilution the suffix “Dil” (clause 8) |
| Sample container | clear colourless glass; referee — the jar in Figure 1; routine — a cloud and pour point jar: internal diameter 30–32.4 mm, height 115–125 mm, wall up to 1.6 mm; filled to at least 50 mm (5.2, 6.1) |
| Light source | 2750 K lamp (quartz halogen 3300 K) with daylight filter and opal glass; background brightness 900 ± 100 lx (A.2) |
| Precision | repeatability 0.5, reproducibility 1 colour number (clause 9) |
Standard
- Standard number
- PN-ISO 2049:2010 (Polish version; adopts ISO 2049:1996 [IDT])
- Title (PL)
- Przetwory naftowe — Oznaczanie barwy (skala ASTM)
- Title (EN)
- Petroleum products — Determination of colour (ASTM scale)
Step-by-step procedure
-
Preliminary examination — liquid products
The sample container is filled to a depth of at least 50 mm. A hazy sample is heated to 6 °C above the temperature at which the haze disappears, and the colour is determined at that temperature (6.1).
-
Preliminary examination — waxes and petrolatum
The sample is heated to 11–17 °C above its melting point (6.2).
-
Samples darker than 8.0
15 volumes of sample (wax — melted) are mixed with 85 volumes of kerosine at the same temperature, and the colour of the mixture is determined (6.1–6.2).
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Preparing the colorimeter
Two (two-field colorimeter) or three containers (three-field) are filled with water to at least 50 mm and placed in the compartments; with the light source switched on it is confirmed that, without the standards, the light intensity through all compartments is equal (7.1).
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Measurement
The sample container is placed in the sample compartment, the water-filled containers in the standards compartments, and the cover is put on. In a three-field colorimeter the sample is bracketed by a darker and a lighter standard or by an exact match and a darker one; in a two-field instrument the matching standard is chosen, or if no exact match is possible, the next darker one (7.2–7.3).
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Result
The number of the matching standard is reported, e.g. “7.5 colour”; an intermediate colour — the number of the darker standard with the letter “L”, e.g. “L7.5”; a sample darker than 8 — “D8”; a result after dilution — with the suffix “Dil” (clause 8).
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Colorimeter | light source, glass colour standards, sample container housing with cover and viewing piece; two-field or three-field, with fields of view according to A.1 (5.1) | — |
| Artificial daylight source | lamp of colour temperature 2750 K (quartz halogen 3300 K), daylight filter glass and flashed opal glass; background brightness 900 ± 100 lx, free from glare and shadows (A.2) | — |
| Glass colour standards | according to Table A.2 of the standard, width at least 14 mm (A.3) | — |
| Sample containers | clear colourless glass; referee according to Figure 1, routine cloud and pour point jars (5.2) | — |
| Sample cover | dull black inside, excluding exterior light (5.3) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Water | — | grade 3 according to ISO 3696, colour not greater than 10 Hazen units according to ISO 6271 — for the containers in the standards compartments (4.1, 7.1) |
| Kerosine | — | lighter in colour than a solution of 4.8 mg of anhydrous potassium dichromate in 1 l of water — for diluting samples darker than 8.0 (4.2) |
| Potassium dichromate | 7778-50-9 | anhydrous, according to ISO 6353-2 — for the comparison solution for the kerosine (4.2) |
Health and safety (OHS)
- The standard warns that its use may involve hazardous materials, operations and equipment, and that the user establishes the safety and health practices (warning before clause 1)
- Potassium dichromate for the comparison solution is toxic — according to its safety data sheet
- Heated samples and kerosine are flammable — according to their safety data sheets
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-ISO 2049:2010 (Polish version; adopts ISO 2049:1996 [IDT]) — “Petroleum products — Determination of colour (ASTM scale)”.
How does this method work?
A test portion in a clear colourless glass container is viewed in a colorimeter under an artificial daylight source and compared with glass colour standards; containers filled with water stand in the standards compartments, and the whole is covered with a cover that is dull black inside, excluding exterior light. The matching standard, or the one closest to it on the darker side, is recorded (clauses 3, 7).
What is the measuring range and accuracy?
Scale: glass colour standards up to 8.0; darker samples — after dilution with kerosine (15 + 85) or the result “D8” (6.1, clause 8); Reporting: number of the standard, e.g. “7.5”; intermediate colour — letter “L” and the darker standard, e.g. “L7.5”; after dilution the suffix “Dil” (clause 8); Sample container: clear colourless glass; referee — the jar in Figure 1; routine — a cloud and pour point jar: internal diameter 30–32.4 mm, height 115–125 mm, wall up to 1.6 mm; filled to at least 50 mm (5.2, 6.1); Light source: 2750 K lamp (quartz halogen 3300 K) with daylight filter and opal glass; background brightness 900 ± 100 lx (A.2).
How long does the test take?
The procedure comprises 6 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Colorimeter, Artificial daylight source, Glass colour standards, Sample containers, Sample cover.
Where is this test used?
Lubricating oils, heating fuels, diesel fuels and petroleum waxes, including petrolatum (clause 1, 6.2); Only products without artificial dyes (clause 1); Manufacturing control — colour may indicate the degree of refinement or contamination with another product (ASTM D1500).
What safety precautions apply?
The standard warns that its use may involve hazardous materials, operations and equipment, and that the user establishes the safety and health practices (warning before clause 1); Potassium dichromate for the comparison solution is toxic — according to its safety data sheet; Heated samples and kerosine are flammable — according to their safety data sheets.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-ISO 2049.