Garment dyeing

Service & Technik Informationen

Garment dyeing Sewing thread and sewing recommendations

for

the

sewing

industry

Garment dyeing – Sewing thread and sewing recommendations Some call it garment dyeing, others speak of PPT (Pronto per Tinta), others PAT (Pret a Teindre) or RFD (Ready for Dyeing) – but they are all talking about the same thing: They speak of garments that are sewn "raw" and dyed after sewing. They are usually made of natural fibres, for the most part cotton, and for specific applications polyamide as well. Garment dyeing is currently very fashionable; not very many collections do without it, especially for trousers. Its unmistakable look and its matchless character are much valued. At the same time, garment dyeing allows high level of flexibility regarding colours, with great advantages in logistics, materials management, and supply.

Sewing threads for garment dyeing With regard to the sewing thread, special considerations are necessary to keep the quality of the seam at the usual standard. The question of which will be the right thread for garment dyeing cannot be easily answered. There are different options – each with its own advantages and disadvantages. These should be known in detail to be able to choose the right sewing thread concept for a specific application. The detailed information contained in this AMANN S+T brochure will make this decision much easier. The standard sewing thread concept for a “normal” production utilising polyester sewing threads does not make much sense for garment dyeing – unless you are prepared to determine the colour of the sewing thread way in advance. Then what is done is you sew natural white material to be dyed in red later with a red sewing thread, for example. Then, the seams and the sewing features will be of the usual quality, but the flexibility as regards colour, and thus the actual advantage of garment dyeing is lost. For some producers with an awareness for quality, this can be the right way to go especially if the batches to dye are small and produced sporadically, as is the fashion, and therefore it is really not worth looking for better alternatives. For all other producers, however, this solution is not very reasonable. So, they will be looking for alternatives: Sewing threads with good dyeing properties in connection to the material. An obvious solution here is the cotton thread range. But Lyocell and polyamide sewing threads are an option too. AMANN maintains all three product ranges and has developed other solutions in addition to standard cotton threads, for the benefit of improved seam quality. Many things are happening in this sector – well-known standards and possible concepts are presented in the following.

Garment dyed trousers – trendy season after season

From a production point of view, garment dyeing is very challenging. The change in conventional work processes has consequences for sewing: materials and accessories that are used are changing and thus also reliable processing and quality indicators, therefore production parameters must adapt. Raw materials used for garment dyeing have usually received some finishing (for example: desizing, singeing, or sanforizing) to prepare them for the subsequent dyeing processes and to facilitate sewing. All the accessories like sewing threads, zippers, pocket linings, labels, rivets, etc. must be suitable for the special requirements of the subsequent dyeing process and finishing. Each accessory's suitability must be tested in detail. Will the label be readable after dyeing? Will the zipper tape take up the colour? Will the rivets survive dyeing without any unwanted colour changes? ... These issues must be clarified in prior tests, because the dyeing and finishing conditions are often not actually known and they can only be evaluated in practical tests.

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Cotton threads The use of cotton threads has been the usual standard for garment dyeing so far. When cotton materials are sewn with cotton threads, then the later dyeing process is no problem. AMANN offers the following cotton threads for garment dyeing: MERCIFIL 12 CORNETA 24/2 MERCIFIL 40 MERCIFIL 50 CORNETA 24/2

MERCIFIL 40

MERCIFIL 50

AMANN cotton threads for garment dyeing – an overview of ticket numbers

When choosing the suitable count, the ticket number system must be taken into consideration too. The count of a MERCIFIL 50 thread cannot be compared with the count of a SABAC 50 or RASANT 50 thread. With cotton threads, the ticket number is usually stated in NeB (Number English Baumwolle (= Cotton). The following table shows how the ticket numbers of AMANN cotton threads translate into the usual ticket numbers in the industry. It also states the appropriate colour numbers. Ticket number AMANN cotton threads

Count (Nm)

Count (dtex)

Ticket number commonly used in the industry

Colour number

MERCIFIL 50

53/2

189 x 2

Between No. 80 and No. 100 3000 or 6231

The use of cotton threads in garment dyeing seems so simple and natural that an associated drop off in seam quality is often underestimated or overlooked. In fact, important quality factors like tensile strength, abrasion resistance, and elongation of cotton threads area incomparable to industry-standard polyester corespun threads! The diagrams 1, 2 and 3 demonstrate at a glance the extreme differences in quality.

Comparison in tensile strength 4500 4000 3500 Tensile strength (cN)

MERCIFIL 12

CORNETA 24/2 in special colour 6231 that washes out – never a cause for confusion.

3000 2500 2000 1500 1000

MERCIFIL 40

43/2

233 x 2

No. 80

3000 or 6231

CORNETA 24/2

26/2

385 x 2

No. 35

3000 or 6231

MERCIFIL 12

25/3

395 x 3

No. 25

0001

Translation of cotton thread ticket numbers into ticket numbers common in the industry, plus AMANN colour numbers for garment dyeing.

500 0

CORNETA SABAC 35 24/2

MERCIFIL SABAC 80 40

Diagram 1 – Comparison of linear tensile strength: Cotton thread MERCIFIL or CORNETA / PEScorespun thread SABAC (Test in accordance with DIN EN ISO 2062)

The cotton threads used for garment dyeing are usually not natural undyed cotton, because depending on their origin the actual colour can differ, sometimes they are yellowish-grey. At least with lighter colours, for example pastel tones, this can have an influence on the dyeing results. Therefore, the cotton threads are usually dyed in a standardised natural tone (colour number 3000). To avoid any confusion – natural coloured polyester threads should by no means be used mistakenly because the seams would remain natural white after dyeing – we recommend using coloured cotton threads for this special purpose. AMANN has developed the special-purpose colour 6231 – an uncommon light green. Practice has proven that this is a safe method to prevent confusions. This colour washes out at the beginning of the dyeing process so as to not impair the dyeing in the required colour tone for the article.

This noticeably lower tensile strength has a direct effect on the seam breaking strength, which is reduced: this is a problem for all seams that are exposed to greater stress, such as the back seams on trousers. In some cases, seam breaking strength can be reduced to a level where a seam will even break by manual force.

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Comparison in abrasion resistance

Comparison in elasticity The significantly lower elasticity of cotton threads compared to polyester threads has a noticeable influence on their sewing characteristics and seam elasticity. In today's production environments – sometimes fully automated with high sewing speeds – the use of cotton threads is difficult. Concretely, this means a large number of thread breaks if the machines have not been set correctly. Absolutely critical is the use of cotton threads on multidirectional automated machines, for example to sew on back pockets on trousers, or on very old sewing machines that work with extremely high thread tensions. So, if the problem of sewing cotton threads has been solved, the next problem is low elasticity. Dyed parts of garments sewn with cotton threads show an extremely low seam elasticity at all seams – which is a problem, when the material itself is elastic. The results are broken seams under slight stress when worn.

45.000

Abrasion resistance (Touren)

40.000 35.000 30.000 25.000 20.000 15.000 10.000 5.000 0

CORNETA 24/2

SABAC 35

Diagram 2 – Comparison in abrasion resistance: Cotton thread CORNETA 24/2 PES-

20

corespun thread SABAC 35 (Abrasion test with Martindale tester on dyed seams)

18 16 Elongation at break (%)

Special attention should be paid to this abrasion resistance comparison. A low cotton thread abrasion resistance is the biggest problem regarding seams in the garment dyeing industry. First the mechanical stress during the sewing process and then during the dyeing and finishing processes and lastly the normal wear and tear on the garment – this is really hard on cotton threads. Worn out and open seams, especially at heavily exposed areas, is the result.

14 12 10 8 6 4 2 0

MERCIFIL 40

SABAC 80

Diagram 3 – Comparison of elongation at break: Cotton thread MERCIFIL 40 / PES corespun thread SABAC 80 (Test in accordance with DIN EN ISO 2062)

Frequent quality problem areas in garment dyeing: Fraying seams at heavily exposed areas such as ornamental seams on back pockets or bobbin thread loops at trouser waist bands.

The quality-relevant differences are increased by dyeing and finishing process stress. While polyester sewing threads survive the dyeing process almost unharmed, cotton threads are additionally damaged by each individual process. Depending on the dyeing conditions, the drop off in quality is sometimes significant. It is not surprising that dyed garment parts often show damaged or destroyed seams, even when brand new. A large portion of second quality goods, many complaints, and the resulting loss of reputation are a logical consequence. To keep the difference in quality as low as possible, coarser than usual threads should be chosen when determining the sewing thread concept. The size concept must be worked out individually, depending on the product group, the seam concept (seam type and stitch type), and the stress, to which the thread is exposed during the dyeing and finishing processes. The following table offers some orientation here.

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Product group

Sewing thread concept Closing seams

Topstitching seams**

Trousers, skirts, jackets

MERCIFIL 40*

Lock stitch: (stitch type 301) MERCIFIL 12 CORNETA 24/2 (Needle thread) MERCIFIL 40 (Bobbin thread)

Shirts, blouses, dresses

MERCIFIL 40 or 50 for finer materials

T-Shirts

MERCIFIL 50

Edge-finishing MERCIFIL 40 or 50 for finer materials

MERCIFIL 40 or 50

MERCIFIL 50

MERCIFIL 50

MERCIFIL 50

* For closing seams exposed to greater stress, we urgently (!) recommend an additional topstitching seam to ensure a sufficient cross-resistance of the seam. ** Chose the thread with the best decorative effect. Size recommendations for garment dyeing, for sewing with cotton threads

One option for this sewing thread concept worth considering is the use of cotton-polyester corespun threads for all closing and joining seams that are not visible. The use of RASANT (in the colour 0003) would be extremely beneficial for seam quality. Tensile strength, abrasion resistance, and elongation of closing and holding seams would be of the same high quality. However, the dyeing results would be rather imperfect:

Seams tinged with grey due to the polyester core of cotton corespun threads

The polyester core of corespun thread does not take up dye; this is why the seam is tinged with grey if cotton corespun threads are used in garment dyeing processes. Every producer must decide if such a seam look is acceptable for inside seams in favour of optimal durability. Considering the quality problems when using pure cotton threads, this option should not be opted out too quickly.

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Sewing recommendations Assuming cotton threads to be the standard sewing threads in garment dyeing, their selection and adhering to production parameters are of utmost importance. Firstly sewing conditions must be adjusted to the special sewing properties of cotton threads, and secondly critical seam quality must be optimized as far as possible. The following overview shows the most important recommendations.

Stitch density The stitch density has a direct influence on the cross-resistance and seam elasticity, the weak points of garment dyeing. Seams that will be subjected to a high level of wear and tear should therefore be sewn with a higher stitch density than usual. Exact parameters must be determined for each sewing operation (seam and stitch type) individually. For finishing the cut edges, a minimum stitch density of 4 stitches/cm is required to prevent fraying during the dyeing and finishing processes.

Thread tension The correct thread tension is the key for ensuring even seams and a satisfactory seam stability and elasticity. It should be as low as possible to achieve the proper thread distribution from needle and bobbin thread.

Stitch and seam type Not every stitch type or every seam type is suited for every sewing operation. With respect to the seam breaking strength, the simple lock stitch closing seam or a double chainstitch is the weakest solution. Depending on the sewing thread concept and sewing operation, this sewing method should not always be applied. For example, when using MERCIFIL 40 for needle and bobbin thread to close a back seam on trousers, this simple closing seam is absolutely unsuitable. Here, it is necessary to add a topstitched seam to increase the seam breaking strength to the required level. In general, a topstitched seam significantly improves the seam breaking strength. 2-needle-topstitching or sewing operations, especially felled seams, are beneficial for seam breaking strength, but at the same time aggravate the problem of seam pucker.

Under the aspect of seam elasticity, however, double chainstitching is to be favoured. The greater thread reserve provides a better seam elasticity. Lockstitching cannot provide sufficient seam elasticity required for the processing of elastic materials, not even with a sufficiently high stitch density and low thread tension. For a proper inside workmanship of a garment piece, we recommend using seam types such as felled seams, cased seams or bound seams. The various advantages and disadvantages of the various stitch and seam types prove once again how carefully and individually they must be determined for each sewing operation.

Choosing the needle For the AMANN cotton threads we recommend using the following needle sizes: MERCIFIL 12

Needle size Nm 110-130

CORNETA 24/2


MERCIFIL 40


MERCIFIL 50


The precise adjustment and selection of the suitable needle point must be done keeping the material and the sewing operation in mind. To avoid fabric damage by needle penetration – a common problem in garment dyeing – the needle should always be as fine as possible. It has proven beneficial even to use rounded needle points (FFG or SES) for delicate materials. Above sewing recommendations also apply for the use of Lyocell threads. It is just as important for these to improve the seam quality by choosing the best suited sewing parameters. Polyamide sewing threads, of course, are different: For these, you can use your standard sewing parameters. There is no need to adjust the sewing conditions for reasons of quality. Only their greater elongation, compared to standard polyester sewing threads, can to some extent require an adjustment of thread tension.

Experience in practice has shown that double chainstitching is more susceptible to stress in the dyeing and finishing processes than double lock stitching. Since the looping of needle and bobbin thread occurs outside the material plies, the looping points of double chainstitching, especially the pointed loops visible on the underside of the material, are more susceptible to damage. This behaviour must be given special consideration when determining the waist band seam on jeans, which in general is a very critical seam with respect to abrasion. The waist band seam in pre-dyed garments should not be sewn with double chainstitching.

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Amann & Söhne GmbH & Co. KG Hauptstraße 1 D-74 357 Bönnigheim Phone +49 (0) 71 43/277-250 Fax +49 (0) 71 43/277- 460 [email protected] www. amann.com

All facts and figures are intended exclusively for your information All recommendations presuppose adjustment of the sewing conditions to the appropriate sewing fabric.

101971 GB02000046