Laser compatible paper and ink

Let me preface this by noting that I was a laser printer engineer for Hewlett-Packard in the early 1990’s, so I have some familiarity with the technology.

It is important to understand how laser printers work in order to answer this question. In a nutshell they work similar to offset printing.

1. There is a roller inside the press. A the printer translates your page into a raster (series of dots in horizontal lines like a TV screen or computer monitor) the laser “paints” the image onto the roller, charging it with static electricity in those areas that will be black.

2. The roller is run through the toner. Toner is microscopic plastic particles which are pigmented black (or C, M, or Y if using a color laser — each is applied in a separate pass). The static on the roller picks up the plastic particles.

3. The paper is run through a static charge that makes the paper the static charge inverse of the image on the roller. When the image on the roller comes in physical contact with the paper, the image/toner is transferred to the paper with static. The roller is “scraped” to neutralize the charge and eliminate stray toner, and the process starts again. The average 8x11 page may have 3 passes of the roller, so all of this painting, transferring, and scraping is happening in real time as the page feeds.

4. The paper is run through the fuser. This is basically a high heat mechanism which melts the plastic toner to the page.

5. The paper is run through a static neutralizer, and ejected.

As a printer engineer you struggle with several variables.

1. Smaller toner means higher resolution images, but it also increases haloing, static pickup of stray particles which spot the page, etc… so there are some limits.

2. Higher heat means better fixing on the page, it also leads to increased paper curl, paper jamming, energy waste, etc…

3. Static is the friend and the enemy. At higher speeds, you have less ability to dissipate static. A problem everyone encounters on high speed copiers (static making the ejected stack of paper hard to jog, etc…)

OK, long preface, but important to understand how laser printing affects things.

First thing to consider is the smoothness of the paper. Typical office paper is pretty smooth. This is by design. The smoother the surface, the more precise you can get the image transfer, and the higher resolution/crisper output you can get. In reality, under high magnification, office paper is quite rough, with peaks and valleys. Wherever there is a valley, you are likely to skip toner transfer just like the problem with printing ink on rough paper with large solids. You get “mottling” or “skipping”. It not only affects the image transfer, but the fusing as well, as it takes relatively more heat to get the paper hot enough to fuse the toner. For example, feed a sheet of relatively rough paper (100% cotton, lettra letter, etc…) through your printer and then look at it under magnification. You’ll see skip. Also, rub the toner aggressively with your thumb and you’ll see some rub-off as the toner hasn’t fully fused. Print the same sheet with office bond. You’ll see more accurate toner transfer, and due to the thin weight of the paper and smooth surface, better fusing of the toner. You typically can’t rub it off with your thumb. That is the “gold standard” for printer engineers and we build printers to fix toner in that range.

Laser Printers typically allow you to define if you are feeding thicker paper with several paper handling settings. If you set the printer to print envelope, or to print a “thicker” paper, it will increase heat and slow down feed speed accordingly to increase the temperature of the paper and increase fusing/melting of the toner.

The “best” quality paper for business correspondence is 25% cotton. It gives a “feel” to the paper but keeps it relatively smooth for good resolution and fixing of the toner.

OK. Now back to the letterpress world.

When you print letterhead, if the ink isn’t fully fixed on the paper, when it comes under the fuser, the ink can partially reconstitute. When that happens, it transfers printing ink to internal rollers and components on the printer. These then destroy internal scrapers and components over time, reducing the life of the toner cartridge and various consumables in the printer. In the worst case, the reconstituted ink can actually offset onto following pages, or even further down on the same page.

This is a significant problem for inks that are high in waxes, which don’t fully evaporate during drying. High gloss inks for example.

Some inks dry harder and are less susceptible to the flexing, bending, and high heats found inside a laser printer or copier. Soy based inks tend to dry quite hard, and are fully evaporated after 72 hours and work the best for this. High wax content inks should be fully avoided. Rubber based inks theoretically don’t dry, but are instead absorbed into the paper. Depending on the quantity of ink used it is theoretically possible that some rubber ink could come onto the rollers in a printer after being heated.

In my print shop here, I always use soy for letterhead. Chances are you’re fine with most oil based inks, but I’m more conservative. Large solids on a letterhead/logo increase the likelihood of problems because you’ll use more ink to get coverage, leading to less efficient drying on the paper.

I’ve printed letterhead on 100% cotton with no problem. I print it on a higher heat setting so that the toner doesn’t offset after the letter is folded and in the mail.

My recommendation for most clients is to choose one of the 24# 25% cotton bond watermarked papers for business correspondence. People like lush, thick, papers, but in reality they don’t print well on lasers or inkjets (inkjets have a problem called “wicking” where the ink strays down the length of a paper fiber, making printing “fuzzy”). Paper manufacturers will tell you if their paper is laser/inkjet safe. Follow those recommendations closely. They work with printer manufacturers to eliminate all the variables mentioned above. If your client writes with a fountain pen, then the wicking problem also applies to paper used in letterhead and can be a real problem. Inkjet safe papers typically work well with fountain pens.

Net/net, I generally don’t recommend Lettra letter or other 100% cotton papers for this type of work. I’ve used it, and have some personal letterhead done on it, but you face technical problems in getting correct printing on the laser printer that most users won’t fully understand and face getting frustrated over. Of course, little of this will matter with clients who want what they want, so we go ahead and do what they want because they are paying for it.

Long answer, hopefully useful.

Alan

The laser printer has a high-temperature fuser designed to stick the toner to the paper. I’ve heard that rubber based ink will melt and wreck the fuser.

70# Text French Poptone runs great in my Brother laser printer.

Alan, did you invent the Laserjet 4? That thing is a beast.

I worked on the Laserjet 3, 4, and 5 series while working in Boise Idaho, and then transferred to the division in Palo Alto, California working on 40ppm+ printers for data centers. My role was PCL and Postscript driver engineering. These days, I do corporate strategy work. I always felt that the 4 series was probably the apex of the laser printers put out by HP. They were overbuilt and many are still in use today.

Wow. Fantastic response.

French emailed me and said any of their text weight papers are laser and inkjet guaranteed.