Colourfastness to Light

Purpose
This method is intended to determine the resistance of the colour of textiles to fade when exposed to artificial light (xenon arc) which is representative of natural daylight.

Principle :
A specimen of the textile to be tested is exposed to artificial light under prescribed conditions, along with agreed standards (blue wool reference).
The colourfastness is being assessed by comparison of the colour change of the exposed portion to the masked control portion of the test specimen using gray scale or blue references used.

Equipment

Megasol
Xenotest Alpha High Energy
Xenotest 150 s+ Light Fastness Tester
Xenotest 150
Xenotest 150 s
Apollo
Atlas Ci3000+ Weatherometer/Fadeometer
Alpha LM
All the above operate with Xenon Arc at colour temperature 5500 to 6500K
Supply of masks for partial covering of specimens
Supply of white card OBA Free
S.D.C. Blue Wool Reference standards identified 1-6 or 8 if specification requires
Humidity test control fabric – red azoic dyed cotton
Mounting Card without OBA
‘Black Panel’ thermometer
or
Standard black thermometer
Colour Assessment Cabinet
Grey scales for colour change
Grading Mask
color fastness to light test eqipment

General Instruction
• with 40% relative humidity
• maximale Blackstandard temperature 50°C
• blue wool references 1-8 for Europe have to be used;not L2-L9 for US

Specimen Preparation

Avoid specimens within 5cm of the selvedges.

Cut a specimen not less than 45mmx 20mm

For multi-coloured fabrics, prints or stripes, all the colours of the design should be included. This may require cutting a larger specimen or several specimens.

Cut the OBA Free card to exactly fit the specimen holder, or use pre cut card.
Staple the specimens face side up onto the OBA free card.
With each batch of specimens to be tested, mount one set of blue wool standards in sequential order from 1 to the light fastness performance requirement.
Each blue wool standard should be no less than 20mm x 45mm

eg.

for specimen fastness requirement to grade 4, use blue standards 1-4
for specimen fastness requirement to grade 5, use blue standards 1-5
for specimen fastness requirement to grade 6, use blue standards 1-6

NB. The same card can be used for both the specimens and standards.

color fastness to light specimen preparation

Test Procedure

Light Fastness to required blue wool standard – Intermediate Exposure/Final Exposure

Large numbers of specimens can be tested simultaneously against a single set of Blue Wool Reference standards

a) Place the card mounted with specimens into the specimen holder and cover with the exposure mask which covers the centre one-third portion.

b) Place the card with the blue standards into the specimen holder and cover with the exposure mask which covers the centre one-third portion. See Diagram Fig 1

c) Place the holders into the light fastness tester. Fill empty holders with OBA free card.

d) Expose the specimens and blue standards, and frequently inspect in a colour matching cabinet under D65 light using the grading mask, until the exposed area compared with the unexposed area of the second highest numbered blue standard has faded equivalent to grey scale 4. (Intermediate Exposure)color fastness to light test Exposure Procedure
eg.

- For light fastness performance of 4, expose blue standards 1-4 until blue standard 3 has faded to grey scale 4

- For light fastness performance 5, expose blue standards 1-5 until blue standard 4 has faded to grey scale 4

- For light fastness performance of 6, expose the blue standards 1-6 until blue standard 5 has faded to grey scale 4.

e) Re-cover the specimens and blue wool standards with the mask which covers the left two thirds. See diagram Fig.2

f) Continue to expose and frequently inspect in a colour assessment cabinet under D65 light using a grading mask, until the 2nd exposed area compared with the unexposed area of the highest blue standard has faded equivalent to grey scale 4. (Final Exposure)

g) At this point remove the specimens from the light fastness tester for assessment in the colour assessment cabinet under D65 light, using the grading mask.

color fastness to light test Procedure

Important Notes:

1. The above method of exposure is the preferred, most frequently used method. However, the use of alternative masks which allow intermediate/ final ratings to be made is acceptable.

2. SDC Blue Wool Standards are NOT equivalent to light fastness standards L2-L9 produced in the U.S.A. The results obtained are not interchangeable.
Assessment of the specimens
to avoid misrating of specimen due to photochromism, it has to be conditioned at least 24 h in the dark at room climate.
• the assessment has to be done by 2 independent persons; as final result take the average of both ratings
• the assessment (D) has to be done
• 1) defined grey scale
• 2) grey frame same grey colour as background or black frame
• 3) white paper as background
• under defined light D65 with defined angle of 45°
• compare the specimen with the blue wool references
• the grade of specimen is the number of the blue wool reference which corresponds in changes of colour between exposed and unexposed part of the specimen
• use a grey or black frame for assessment
color fastness to light test Assessment

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