BYK Additives & Instruments

Paper Coatings

What makes paper curl and how can it be prevented?

The non-uniform uptake of water or atmospheric moisture on two sides causes the side with greater moisture content to expand; thus curling towards the drier side. Curling is common for papers that are only coated on one side. Curling can be corrected by equalizing the uptake of atmospheric moisture of both sides. For single side coated paper, increasing coating hydrophilicity can minimize or prevent curling.

How do I reduce dot gain?

Dot gain is the increase of the applied ink drop's diameter (ink droplet spreading). One possibility is to reduce the paper surface porosity, another possibility is to increase a little bit the hydrophobicity of the paper (adding wax-based performance additives) or to increase the ink viscosity.

How can I improve adhesion?
Adhesion is a highly complex issue that can be addressed in various ways. Surface tension has two components, polar and disperse component combined. Wetting will occur when liquid being applied is lower in surface tension than the substrate's surface tension. However, wetting does not guarantee adhesion. It is the proper matching of the polar/disperse components of substrate and coating that in turn controls adhesion. Typically, increasing the polar component leads to improve adhesion. Adhesion can be corrected by using adhesion promoters, and polar surfactants. Adhesion is the sum of all adhesive forces; Van de Val, atomic, charge, physical, etc. Since wetting and penetration are events that occur simultaneously when liquids are applied onto porous substrates such as paper, controlling or modifying surface porosity, polarity, roughness, and penetration will effect both wetting and adhesion.
How do I increase water resistance?
Increasing surface hydrophobicity will increase resistance to water uptake and penetration. We use different hydrophobic products to increase water resistance, also to avoid fiber swelling for paper stability. This is used in technical paper, baking paper and packaging paper.
How do I improve abrasion resistance?
Micronized wax-based additives and polyether modified di-methyl polysiloxane surface additives added to your coating formulation will improve coated papers' resistance to physical damage.
How do I select the right defoamer?
The mechanism of defoaming requires destabilization of the lamella, or the foam bubble wall. Defoamers are incompatible with the system, exhibit positive entering and spreading coefficients. This incompatibility must be carefully controlled because too much incompatibility, while exhibiting good defoaming, will introduce other defects into the system. These defects will range from specks and seeds to cratering of subsequent coatings.
I want to improve my surface to have good resistance to burnishing.
Specialized micronized wax based additives added to your coating can prevent low gloss surfaces from burnishing or increasing in gloss from rubbing. The combination of good printability and to avoid glossmottling can be practised in using a low amount of wax-based performance additives.
How do I reduce the mottling of my printed paper?

There are different kinds of mottling but nearly all have the same source: non-uniform liquid uptake. In order to prevent this we are using different wax-based performance additives in order to uniform the liquid uptake.

I have ghosting at my printed papers, how can I get rid of this?
Ghosting on printed paper can have various reasons. One main reasion is back side ghosting by double side printed sheets. This effect will appear when papers have a two sidedness and therefore have a variousity in liquid uptake. The printing ink is applied and not totally dry while another paper sheet is stored above it. Because of the variation of penetration and wetting issue on the different sides of the paper, the backside of the stored paper above the other is sucking more on the ink and therefore a transfere of the ink onto the backside of the following page will happen. For this topic we are using a wax-based performance additive in order to uniform the liquid uptake on both sides of the papers. Another main reason is the opacity of the paper. Here is aonther picutre arrangement the easiest way to solve the problem.