Colourfastness is one of four key topics (others include Abrasion Resistance, Pilling, Seam Slippage) that we are covering to provide some background as to how we test and why.
Test results provide us with critical information about textile’s durability and suitability for certain applications. We externally test all James Dunlop and Mokum textiles in Melbourne at a highly reputable laboratory who are amongst the most conservative and stringent in the world, due to the extremely harsh environmental conditions we face here in Australia and New Zealand.
We have gathered a number of frequently asked questions relating to colourfastness so we asked our Mokum studio designers Stephanie Moffitt and Annie Moir to share their expert knowledge.
One of the most important textile tests is that of colourfastness.
Simply put, a colourfastness test measures how well a textile will resist or withstand fading. Fading typically means a change in colour which may be a change in hue, depth or brightness of colour. We perform a range of different colourfastness tests when developing a new textile, we test its resistance to fading against UV light, as well as washing / dry cleaning and also rubbing.
Can you briefly outline the colourfastness to washing/ laundering test?
Colourfastness to washing and/or dry cleaning measures a fabrics ability to withstand fading or colour loss from laundering. The test replicates specific cleaning methods then measures any colour loss against a set of five grey scales, creating a result (1 being least colourfast and 5 being most colourfast). In this instance, a result of 4-5 is the result we strive for.
One question pops up a lot, if a product is machine washable can it be spot cleaned?
We would always approach spot cleaning with water or a cleaning product with caution. Most of our washable textiles are rating as delicate or gentle washing which means a delicate setting and we would prefer a delicate washing liquid. Whereas spot clean tends to be more localised and more aggressive. If spot clean is needed always first try a dry white clean cloth, to reduce any colour loss as this often can remove a stain.
Can you briefly outline the colourfastness to rubbing test?
Colourfastness to rubbing, or commonly known as ‘crocking’ measures fabric resistance to colour loss when subjected to rubbing or friction from another fabric. This is particularly relevant for upholstery textiles – you can imagine wearing white pants and sitting on a dark coloured sofa, you’d want to be confident that when you stand up your pants haven’t changed colour.
With this test, a white cloth is used as a standard abradant, and rubbed against the test fabric in both in both dry and wet conditions, with wet being more severe. Any colour transfer onto the white cloth, and colour loss from the test fabric is analysed and measured against a set of 5 grey scales (1 being least colourfast and 5 being most colourfast). The result we receive from the lab helps us to determine the recommended usage for the upholstery fabric.
And finally, the most widely coveted colourfastness test, can you explain the colourfastness to light test?
Colourfastness to light measures a fabrics resistance to colour loss due to UV light. The fabric to be tested is put under an artificial lamp in controlled conditions to replicate the effects of natural light exposure. To establish the degree of colour change, the fabric is removed at specific intervals (usually 40 hours for interior furnishing fabrics) and compared to both a piece of the original fabric and also a standard set of ”blue scales” which are also tested in the same conditions.
On our sampling we publish a result of “UV x/x Blue Scale”. What is the blue scale?
The blue scale is a testing card of 8 standard blue wool swatches which are placed in the same light conditions as our “test” sample. The amount of fading of the sample is then assessed by comparison to the original colour, against the blue swatches and their original swatch shade.
A rating between 0 and 8 is awarded based on identifying which one of the eight strips on the blue wool standard card has faded to the same extent as our “test” sample.
The lab access the closest match and assign a test result. This result of 1 through to 8 is what we publish in our product specifications.
What is considered an appropriate colourfastness to light result?
A blue scale test result of 1 indicates almost complete colour loss, so you’d never see a result of 1 on our fabrics, and an 8 is the unicorn result – it doesn’t actually exist! A result of 7 is an extremely high result (indicating no colour loss).
Generally a result of 5 or greater is optimal for drapery fabrics, and 4-5 or greater is considered sufficient for upholstery fabrics.
With that be being said there are a lot of variables that can effect a textiles performance to this test, the composition, the method of dyeing – whether the yarn is solution dyed, whether the fabric is piece dyed or digitally printed – quality of the dye stuff and finishing processes can all impact on the result.
Why is this such a critical test for us in this part of the world?
We have extremely harsh environmental conditions in Australia and New Zealand, especially with regards to the amount of damaging UV light. There is essentially a hole in the Ozone layer above us, so the light is not only abundant, it’s also very damaging without the Ozone filter. Our lifestyle and mild weather calls for transitional architecture that allows for an abundance of indoor-outdoor living. In newer architecturally designed homes, large glass windows are typical, letting in a lot of light. Even textiles that are technically indoors, but on the periphery of the home are subjected to extremely high levels of harsh UV light.
What would you say to those who are afraid of their interior soft furnishings fading?
Everything fades! Including the bricks on your house, paint, your timber floors, and your youth! As we have just mentioned the dyeing method and quality of dye is critical, but in general, synthetic or man-made fibres tend to outperform natural fibres when it comes to resisting fading.
The fibre most resilient to sunlight damage is acrylic, followed very closely by polyester. Of natural fibres, cotton and linen have quite good sun resistance with quality dye stuff, much more than say Silk. But the best fibre type in high sun environments is definitely solution dyed acrylic, olefin or polyolefin.
See our article here on outdoor fabrics.
What tips and tricks can you offer in increasing the lifespan of your textiles in relation to UV damage?
One of the most effective ways in which to reduce UV damage to your interior soft furnishings is the use of a quality curtain lining. Depending on the application and specifics required we have multiple linings in our range.
The leading edges of a curtain (those facing the windows) are the most exposed part and therefore most vulnerable to sunlight degradation. A trick to either hide fading or to slow down the onset of fading when you have two curtains is to swap your curtains– moving the leading edge to now sit against the wall and vice versa.
You can have UV damage from direct and indirect and indirect light – with light bouncing off surfaces within your home. It’s important to engage in regular care and maintenance for your upholstery fabrics too – regular vacuuming but also rotating your furniture within a room and rotating individual cushions too where possible. This of course won’t stop fading from occurring, but it will minimise the appearance by making the fading more gradual and even to the eye.
What’s the key takeaway message on colourfastness to light?
Test results provide a valid guide, however there are many other factors that can contribute to a fabric’s performance insitu which the specifier should always consider – i.e. surrounding environment, proximity to the window, whether the house is North facing, South facing, lifestyle factors such as do they have children or pets, and what are the clients expectations for the level of care and maintenance they are willing to uphold? Are the inherent characteristics of the textiles in line with the clients expectations, how do they want it to look as well as what are their expectations on performance or durability?
Like you would care for a silk shirt or a woollen item, you also have to take care of your interior soft furnishings. Don’t install and ignore!
Written by James Dunlop Textiles – https://jamesdunloptextiles.com/journal/tips-how-to/2020-unraveling-textile-testing-colourfastness