Plastisol Ink – Weights and Measures

Ok so not the most exciting topic in screen printing but we are often asked by customers to give prices for Plastisol Ink by kg, so we thought this is a good opportunity to explain why screen printers should always buy plastisol by the Litre.

With some help from the Colour Matching team we ran a quick experiment, we compared one litre of WPS Cotton White Premium Plastisol and one kilogram of the same ink.  Our Colour Matching experts mix inks to Pantone shades, Ral and BS numbers which all require accurate measurement.

1 Kg of WPS Cotton White Premium Plastisol

1 Litre of WPS Cotton White Premium Plastisol which weighs 1.585 kg

It is very clear that 1 Litre of Plastisol weighs significantly more than a kilogram. This is because plastisol ink has a specific gravity typically 1.1 to 1.4. There are some highly opaque inks like WPS Cotton White being higher.

Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance (normally water) for the same given volume. (Wikipedia).

So Plastisol inks like the WPS Premium Mixing Range and the Sericol Seritone range are lighter than the high opacity inks but because of their Specific Gravity you will still have more ink in a litre than a kg measure.

More inks equals more prints

All of our standard Plastisol inks are sold in Litres (or smaller) unless otherwise stated.

You often see Screen Ink Manufacturers stating that their inks are certified to OEKO-TEX standards. Either that they are certified or that they conform (quite a big difference). So what is OEKO-TEX and what is its purpose?

In 1992 the Austrian Textile Research Institute (OTI) and the German Research Institute founded OEKO-TEX. Its main aim being to provide an objective and reliable product label for consumers. Its aim is to ensure that products posed no risk to health, its moto is to increase ‘Confidence in Textiles’.

OEKO-TEX introduced a testing and certification process which incorporates textile research and testing institutes in Europe and Japan. For an ink (or textile) to achieve certification the manufacturers’ products must be tested and certified to a strict criteria. Areas covered include:-

• Illegal substances such as carcinogenic colourants
• Legally regulated substances such as formaldehyde, plasticizers, heavy metals or pentachlorophenol
• Substances which according to current knowledge are harmful to health. But which are not yet regulated or prohibited by law such as pesticides, allergenic dyes or tin-organic compounds
• Parameters such as colour fastness and a skin-friendly pH-value, which are precautionary measures to safeguard consumer health

If an ink or textile product is certified you should see the product class that it is certified to, the class is based on intended use. So under OEKO-TEX Standard 100 there are the following classes :-

• Product class I:
  Textiles and textile toys for babies and small children up to the age of three e.g. underwear, romper suits, bed linen, bedding, soft toys etc.
• Product class II:
  Textiles which, when used as intended, have a large part of their surface in direct contact with the skin. e.g. underwear, bed linen, terry cloth items, shirts, blouses etc.
• Product class III:
  Textiles which, when used as intended, have no or only a little part of their surface in direct contact with the skin. e.g. jackets, coats, facing materials etc.
• Product class IV:
  Furnishing materials for decorative purposes such as table linen and curtains, but also textile wall and floor coverings etc.

Source: OEKO-TEX website

So is the standard important? The simple answer is YES. If an ink has been certified to a given class we know that it is considered safe for the particular use. Many retailers are now only stocking products which conform to those standards. So if you are screen printing baby clothes it is highly recommended to use inks which has been certified.

Leading ink manufacturers such as FujiFilm Sericol and Magna Colours have invested heavily in producing products which have been certified to OEKO-TEX standards. In economically challenged times it is tempting to purchase the cheapest inks but to ensure quality and safety of products always choose certified either OEKO-TEX or other certified products where possible.

In a future blog article we will be explaining what the other main certifications are and also the certifications for the inks we sell.

We close on Friday 23rd December and reopen on Tuesday 3rd Jan 2022.  The last courier collection is the 22nd December for delivery on the 23th. We would like to wish you a Merry Christmas and a Happy New Year!!!