H
H Factor
It is the area under the curve when relative reaction rate is plotted against cooking time.
Half Fold
The half fold is commonly used for brochures and greeting cards. For cover weight paper, a score is usually required to produce a smooth folded edge.
Half + Letter Fold
This fold is perfect for newsletters. An 11" x 17" sheet folded this way has only one open side and fits into a #10 envelope. The newsletter looks good and is easy to handle.
Half Tone
Picture with gradations of tone, formed by dots of varying sizes in one color.
Handmade Paper
A sheet of paper, made individually by hand, using a mould and deckle.
Hard Cook
Undercooked pulp with respect to target conditions.
Hard Pulp
Chemical pulp with a high lignin content.
Hard Sized Paper
Paper treated with high degree of internal sizing.
Hardwood
Wood from trees of angiosperms class, usually with broad leaves. Trees grown in tropical climates are generally hardwood. Hardwood grows faster than softwood but have shorter fibers compared to softwood.
Head Box or Flow Box or Breast Box
The part of the paper machine whose primary function is to deliver a uniform dispersion of fibers in water at the proper speed through the slice opening to the paper machine wire.
Heart Wood
The dark colored , center of a tree trunk, consisting of dormant wood.
Heat Embossing/Thermography
Heat embossing is done with embossing powder and a heat tool. The powder becomes liquid when heated and then quickly dries hard when it cools. The end result of heat embossing is a raised surface on the paper. This process is actually called "thermography" in the printing world.
Heat Set Web
An offset printing process done on a web of paper supplied in a roll. The term heat set originates from the inks used in the process. They contain high amounts of solvent flashed off in ovens to dry at very high speeds. Web presses perfect or print both sides of the sheet simultaneously.
Heat Transfer Paper
The paper used in Thermal transfer printing (Sublimation printing).
Hemicellulose
A constituent of woods that is, like cellulose, a polysaccharide, but less complex and easily hydrolysable.
Herbaceous Plants
Non-woody species of vegetation, usually of low lignin content such as grasses.
Hickey
An irregularity in the ink coverage of a printed page. Hickeys are caused by paper or pressroom dust, dirt, or pick out on the printing blanket, all of which prevent the ink from adhering to the paper surface.
High Finish
Smooth finish applied to paper to improve the printing surface.
Hog Fuel
A mixture of bark and other wood waste usually produced by sawmills; burned to produce energy and steam.
Hogged Paper
Paper that has been mechanically torn or ripped to reduce its original size.
Hold Out
Resistance of paper surfaces to the absorption of ink. High Hold Out offers higher resistance to ink absorption. Regular Hold Out allows greater ink absorption.
Holocellulose
The total carbohydrate fraction of wood — cellulose plus hemicellulose.
Hologravure
Printining process by which great continuous 3D depth is achieved using textures and patterns.
Hood
A hood covering the paper machine drying section and designed for moist air removal.
Hot Melt
A type of glue or adhesive applied while hot/warm.
Hot Groundwood Pulp
Mechanical pulp produced by grinding logs that have been pre-treated with steam.
Hydration
The prolonged beating or refining of cellulose pulp in water to reduce it to a semi-gelatinous mass.
Hydrogen Peroxide Bleaching
A method in which pulp is bleached in an alkaline environment with hydrogen peroxide (H2O2), sometimes using oxygen reinforcement. The method considerably reduces the need for chlorine-containing chemicals in the final bleaching of chemical pulps.
Hydrophilic
Having strong affinity for water.
Hydrophobic
Lacking affinity for water.
Hydropulper
An equipment used to slush broke/paper in to pulp.
Hygroexpansivity
That property of a material which causes it to expand or contract when its moisture content is changed; as in paper, when the relative humidity of the surrounding atmosphere is changed.
Hygroscopic
Having the property to absorb water vapor from the surrounding atmosphere. Most of the papers (except glassine, greaseproof or wet strength etc.) are hygroscopic in nature.
Hysteresis (Paper moisture)
That property of cellulose fibers, and therefore paper, that allows the percent moisture content at equilibrium with a specified relative humidity, to be dependent upon the most recent past relative humidity exposure; as if paper had a "memory," with the equilibrium moisture content closer to the most recent higher or lower relative humidity exposure, i.e., two pieces of paper that were last exposed respectively to high and low relative humidities, will have higher and lower moisture contents when brought into equilibrium at 50% relative humidity; dimensions will also vary accordingly.
