- Gel pen
A gel pen uses ink in which
pigment is suspended in awater -basedgel . [ [http://pubs.acs.org/isubscribe/journals/cinnov/31/i09/html/09lw.html The Last Word: Just for the gel of it] ] Because the ink is thick and opaque, it shows up more clearly on dark or slick surfaces than the typical inks used in ballpoint or felt tip pens. They can be used for many types of writing and illustration.The general design of a gel pen is similar to that of a regular
rollerball pen , with a barrel containing the writing mechanism and a cap, and a reservoir filled with ink. The barrels can be created in many different sizes and designs; some have finger grips of rubber or plastic. The size of the nib or pen tip ranges from 0.25 mm to 1.5 mm.Inks
The main advantage of gel ink is its high
viscosity or thickness, which supports a higher proportion of pigments in the medium. The pigments are typicallycopper phthalocyanine andiron oxide s, and the gel is made up of water andbiopolymer s, such asxanthan gum andtragacanth gum , as well as some types ofpolyacrylate thickener s. The pigments are opaque, and gel pens are available in a rainbow of bright and pastel colours, as well as opalescent,metallic , andglitter y colours which show up clearly on dark paper.Ballpoint pen s use a paste ink based on adye solute in analcohol solvent . Compared to ballpoint pens, gel pens:
* Create a bolder line
* Smudge less
* Have occasional skips, due to the ball being less evenly coated with ink
* Use more ink, leading to more frequent refills or replacementsFountain pen s and liquid-inkrollerball pen s use a dye solute in a water-basedsolvent . Compared to these pens, gel pens:
* Are less prone to bleed through to the other side of a piece of paper
* Create finer, more controlled lines with fewer blots
* Can create white or brightly coloured opaque lines on dark surfacesPaint marker s use an oil-based paint/ink that is very opaque and overlays all other colours beneath it. Compared to paint markers, gel pens:
* Are much smaller, with finer tips
* Have no odour and do not require shaking to mix pigment with solventIndia ink (based on carbon black pigment) is perhaps the ink closest to gel ink in opacity, although it is usually made with an alcohol andshellac -based binder.Another trait of gel ink is that it resists common laboratory analysis. The
United States Secret Service has maintained theInternational Ink Library for many decades. Because manufacturers change their ink formulas slightly from year to year, thin-layer chromatography (TLC) can be used on ink from traditional pens to trace the manufacturer and date of manufacture of most inks. The pigments in gel ink do not dissolve, and therefore cannot be analyzed with TLC. [cite journal | first = Gerald | last = LaPorte | year = 2006 | month = May | title = An Evaluation of Matching Unknown Writing Inks with the United States International Ink Library | journal = Journal of Forensic Science | volume = 51 | issue = 3 | pages = 689]References
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