Solvent Printing

What is solvent printing?

Large format and wide format printers have been using solvent printing technology since the mid to late 1990’s.  The term solvent refers to ink that doesn’t contain water.  The inks are instead made up from petroleum based substances such as acetone.  Mild solvents and eco solvents which are less harsh generally use Glycol or Glycol Ether but these are slower drying.  Solvent prints are fully waterproof once dry.

Print heads and print method

Piezo print heads electrically charge and spit the inks out. The ink hits the substrate with fine pin point accuracy. Solvent printing is more commonly a higher resolution print method as apposed to UV printing.
Most modern day solvent printers print at around 800-1500dpi and have 100’s of print nozzles per head.  Print nozzles are very fine holes from which the ink is fired onto the substrate.  The print heads norammly print bi-directionally meaning they put ink down in both directions.   Head movement can print unidirectionally i.e.: in 1 direction if required.  Unidirectional printing is slower but gives higher accuracy.  The Ink hits the surface in exactly the same place each pass reducing banding.

Print quality

 Banding is a term for lines in the print which are more noticeable when printing bi-directionally because of the ink firing onto the substrate from a different direction on each pass of the head.
Modern day solvent printers can print on a number of quality settings which are known as passes.  More commonly prints are produced on either a 6 or 8 passes.  This pass rate can be increased up to 24 passes which increases quality and resolution dramatically. More passes increases the time taken to print.
The inks can be printed onto uncoated vinyl and other roll medias.  The solvents soften the material and this allows the pigments to attach to the substrate.  This makes solvent printing much more durable than standard aqueous (water based) inks.  Early solvent printers were unreliable and took a vasty amount of daily / weekly maintenance to keep them running.  One of the first successful solvent printers was the Arizona 180.  The Arizona printed at dpi of 309 used a 6 colour process.  This includes Light Cyan and Magenta to give a higher colour gamut.

Lamination

Most solvent prints on self adhesive vinyl are over laminated to protect the surface of the print from scratches and UV light deterioration.  UV over-laminates cover the whole area of the printed surface keeping it protected and vibrant for up to 5-7 years outdoors in stand weather conditions. In very hot / bright climates this can be reduced to 2-3 years.   The overlaminate also makes applying the vinyl much easier.  This is due to the solvent softening the base vinyl during the print process.
Vinyl vehicle wrap films must be laminated prior to fitting.  The laminate makes up the micron (thickness) of the finished wrap system.  Thickness of a standard wrap film is around 45-50 micron. With the laminate applied this goes up to around 90-100 micron which is an ideal thickness for wrap installation.
All solvent prints must be outgassed prior to the application of the over laminate.  Outgassing is a term used for the degassing of the solvents from the vinyl after printing.  Once the vinyl is printed it should be loosely unwound to allow the solvent gasses to escape from the surface of the vinyl. If the roll is left tight after printing the gasses cannot escape. Failure not to outgas can results in the adhesive side of the vinyl deteriorating.  This is due to the gasses passing through the adhesive side causing failures to the adhesive or ruining the graphics. Outgassing should be performed over a period of 48 hours after printing and then laminated after this time.