silk fabric Archives

14 November 2015

Curtain Fabric Static

Another grey mohair velvet, luscious upholstery

If you are unfortunate enough to have created beautiful curtains that are plagued by static problems then please read on.

Fortunately static is rarely noticed when curtains are hung, this is partly because of the chosen combination of materials and partly also because the weight of the material overcomes the weak power of static electricity. However if you do have this rare problem then you have already invested a lot of time, effort and money into buying curtain material and having them made up and hung. Do you have to start again?

Before answering that dreaded question it is important to understand what causes the problem in the first place. There is little point in re-making the curtains if the same problem is going to happen again.

Static is a natural phenomena. The main way in which static is created is when two materials are rubbed together causing an excess electrical charge on their surfaces. It is not, however, caused by the friction itself and it is not caused because a material is synthetic/man-made.

All materials differ in their propensity to cause static. It takes the properties of TWO materials to cause static; one must be good at giving up ‘electrons’ and the other good at receiving ‘electrons’. The better that each of the materials are at giving/receiving ‘electrons’ then the more static there will be. For any scientists reading, you might remember that this is measured by The Triboelectric Series.

On the Triboelectric Series; hair, wool, glass, nylon and fur are good at giving up electrons. Whereas silk, paper and cotton are at the other end of the scale and are bad at giving up electrons. Conversely; wood, metals, polyester and styrene are bad at attracting electrons whereas at the other end of this side of the scale polyurethane, polyethylene, vinyl/PVC are good at attracting electrons.

Thus a combination of PVC and hair would produce the most static whereas cotton and wood would produce the least. If you think about combing your hair then this should ring true.

Polyester is very similar to gold, platinum, brass, silver, nickel and copper in its static generating properties. Whereas, cotton is one of the lowest materials on the scale.

So the first lesson, bearing in mind the above, is that the choice of materials ie the curtain and the lining are critical. Also any surface that the curtain comes into contact with is important. So the second lesson is to consider the location.

Let’s turn now to how the curtain is made up. An experienced, professional curtain maker should know how to avoid the static problem.

Taking an example of a mixed composition fabric. Let’s say 40% cotton, 40% viscose and 20% polyester. And let’s also say that the material is loosely woven and has movement. Looking at such a fabric an experienced curtain maker would say that the fabric ‘needed taming’ and that a light cotton inter liner should be used. In addition to that the following details should be followed:

• The interlining should be locked in with 3 inch stitches. This should not be knotted;
• At the leading edge the interlining should be serged and locked in;
• The hem should be herring bone stitched. The stitches should not be too large and should not catch the face fabric; and
• Because of the nature of the fabric, the hem should slightly break on the floor.

These are not generic solutions to all curtain static problem. But they should be considered by the curtain maker.

So we have seen that: the choice of material; how the design works when hung; and how the curtain is made up, all have impacts on the creation or dissipation of static.

6 November 201520 April 2020

Fabric Treatment Companies – FR Flameproofing

We are often asked to recommend fabric treatment companies for flame retarding in contract installations. Most treatment companies offer other services such as; back coating fabric for walls and stain resistance/repellency. There are several such companies in the UK and at various times we have used all of the following:

Essex Flameproofing,

Textiles FR, and

TEK Treatments

Just click the company name to take you to their web site. Please feel free to add comments to this posting recommending any suppliers you have used but any negative comments about other companies are not permitted on this site. Thank you.

19 July 20108 May 2020

What is BS5867 / BS 5867 part 2 type B? type C?

BS5867 part 2 type B is a contract standard for fire retardancy for CURTAINS.

As an interior designer you do *NOT* need to understand the details of the test nor the performance criteria that needs to be achieved.

However interior designers are responsible for the project/installation and because this is a serious are concerning fire risk you DO NEED to:
– Be certain what standard is required for your project/installation;
– Know that you are specifying fabric that meets the appropriate standard; and
– Prove that the fabric you have installed is up to the job.

So here is what you need to do to achieve that, essentially what you need to do to do your job and to ensure you have covered the bases of your responsibility.

1. Determine the fire retardancy standards that need to be adhered to. This may involve contacting the local fire officer. Determine what documentation you need to provide them.

2. Liaise with your fabric supplier to determine if the fabric either:

– inherently meets the standards; or

– requires treatment.

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3. On purchasing the fabric, specify the treatment required. You would say to the fabric company “Treat the fabric to the contract curtain standard BS 5867 part 2 type B, and provide me with documentation showing this has been done”.

4. What you have done now is to specify what standard of treatment has to be undertaken. By doing that there is no guarantee that the fabric will pass the appropriate test even though it has been treated to a standard where it should pass the test. Normally you will receive a document saying that the fabric has been treated to the standard. THIS DOES NOT MEAN IT HAS PASSED THE STANDARD. You need to determine if you want your specific batch of fabric to be specifically tested (after treatment). For larger projects, this will almost certainly be prudent to undertake. You will need to purchase additional fabric prior to treatment and engage the services of a fabric testing factory (not treatment factory). At the end of that process, you will receive documentation stating that the fabric meets the required standard.

The following test details are not normally required to be known by the designer:

Test method
A sample of the fabric, vertically held, is exposed to a small flame.
For type B (Hotels, etc) the ease of ignition is observed. It is also noted if the flame reaches one any edge of the specimen and/or if any burning pieces of fabric fall down.
For type C (NHS) the fabric is further analysed to see what happens once the flame stops but when the fabric still may be glowing.
NB: The fabric is tested before and after laundering
type B (12 wash cycles at 40°c)
type C (50 wash cycles at 40°c)
Test Performance Criteria
Type B Performance Criteria: The edges must remain completely intact and no burning debris should fall.

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12 May 2009

The Durability Of Silk Velvet For Upholstery

The durability depends on quite a few things: the tightness of the weave; thickness/strength of the yarn & fabric; back-cloth composition and strength; and so on.

Essentially you need to look at the Martindale or Rub Test result for the specific fabric in question. Two silk velvets can be quite different.

As with all velvets a proper cleaning regime is important to extend the life of the fabric.

One of KOTHEA’s silk velvets has a rub test/Martindale of 25,000. This is more than adequate for general upholstery.

2 February 200920 April 2020

Dyes and Pigments in Fabric

A Brief History of Natural Dyes (Mordants)

A dye is a substance that gives colour to the fabric. Usually in a way such that washing, heating or lighting does not change the colour greatly.

Dyes tend to be carbon-based (ie organic in a chemical sense) whereas pigments are very fine powders ‘dissolved’ in a liquid. Pigments generally give brighter colours and are man-made.

Dyes have existed for at least 4000 years and, before 1850, were almost entirely from natural sources such as plants, trees and lichens but also sometimes from insects. Here are some natural dyes, rarely used today, and their sources:

1. Yellow
Seeds, stems and leaves of the weld plant
The inner bark of the North American oak ‘quercetin’
Dried petals of false saffron (safflower)

2. Red
Crushed insect bodies from Coccus (cochineal) or it’s distant relation Kermes.

3. Blue
From indigo or woad

4. Purple
From the medium-sized predatory sea snail ‘commonly’ known as Murex.

5. Black
From the middle wood of the Logwood tree. This is still used today to dye silk and leather and is combined with Chromium. I have written other articles about how this ‘natural’ dye is one of the most damaging to the environment because of the use of chromium.

The art of the dye was historically a closely guarded secret with practitioners having their formulae to produce the colours and to retain them by the addition of various metal salts.

Cotton could not be directly dyed whereas wool and silk could. To add a dye to cotton the cotton had to be first treated with salts made from aluminium (red), magnesium (violet), tin, calcium (purple-red), copper, barium (blue) and iron (black-violet) and then dyed. These salts are called mordants.

The Start Of Synthetic Dyes

In the 1850s Chromium was found to give superior dye retention and so started the decline of the natural dye. Chromium mordants are still widely used for wool and less so for silk and nylon.

More precisely, the first commercially successful dye was ‘mauve’ discovered in England in 1856 and taken to market the following year. It was only sold for about 7 years but that was sufficient to start the dramatic decline of natural dyes and the investment in the science for newer and better dyes.

The Chromium discovery meshed well with the Industrial Revolution. The massively growing textile industry in Europe required a cheap and predictable manufacturing process. Natural dyes and mordants could require up to 20 steps in production, the colour could be variable and the dyes had to be transported unreliably from around the world. Because of these factors and the development of chemical science, it is easy to see how by-products of coal tar extraction & coke production, abundant in Europe, became the foundation of the modern dye industry.

By 1900 nearly 90 per cent of industrial dyes were synthetic.

Pre-war (WWI) Germany dominated the commercial dye market accounting for 90% of all output. Many German scientists worked with distilled chemicals from coal tar, an abundant by-product of the industrial revolution at the time. The German success was probably due to their investment in the scientific method and in training scientists themselves. Some further ‘by-products’ of the research include aspirin and saccharin.

After WWI the industry gravitated to Britain (ICI), the USA and Switzerland, also moving away from coal tar to petroleum-based research.

Perhaps only now with the ‘green’ movement are we seeing a resurgence of interest in natural dyes. KOTHEA cautions the environmentally-conscious reader to look carefully at claims of dyes to be natural. Whilst they may well be made from natural materials the processes used along the way can be VERY damaging to the environment.