WRC Exterior Wood Stain 101

Stain and Paint Defined

• Staining is sometimes referred as stain or paint

• Two different uses

• Careful to be specific so no errors

Prime and Paint

• Oil and water based primers for WRC

• Priming seals and prepares

• Film forming, less deep penetrating

• Always opaque

• Lasts longer than stain

Wood Stain

• Not primed first

• Like a paint but different

• Penetrates

• Protects

• Provides color

• Translucent and opaque

• Enhances the beauty

Stain Type Finish Characteristics

SolventProvide a means for the pigment and binder to be applied to a surface

BinderLiterally ‘bind’ the pigment together, and provide paint film integrity and adhesion

AdditivesLow volume ingredients that provide specific paint properties

PigmentsProvide color and hiding properties, and some are used to add body to the paint while keeping manufacturing costs low

Ingredients of Stain

Pigments

Pigments are used in stain to give an aesthetic beauty to wood as well as protect the wood from the harmful effects of the sun.

Stain Pigments

Classifying Finishes

Binders

Acrylic/oil, 100% Acrylic, Hybrid, Alkyd/Linseed oil, and Waterborne Modified Alkyd are some of the different binders used in stains.

These binders are used in stain to help the stain penetrate deep into the wood, seal it, and give it durability.

Binders

FINISHES CAN BE CLASSIFIED BY THEIR VEHICLES OR BINDERS

• Oil Base

• Solvent base (borne)

• Water Base (borne)

• Emulsion

• Oil

• Alkyd

• Varnish

• Acrylic / Oil

• Polyurethane Acrylic / Oil

Stain Type Finish Characteristics

Water

Solvents

Water based (Acrylic/ Oil)

Advantages Disadvantages

Better UV resistance than oil Shorter working time

Fast drying Attention to application detail required

Soap and water clean up

Advantages Disadvantages

Longer working time Fade faster than water based products

Easier application More susceptible to mold/mildew than water based productsHard to clean up – Slow drying

Oil based (Solvent Blend)

Solvent Types

Additives – low volume ingredients that aid in manufacturing, and add specific characteristics to the stain

Paraffin wax – adds extra scuff protection & water beading

Mildewcides – prevent mildew from growing

Reasons to Stain

Reasons to Stain

Do This

Wood fibers absorb and lose moisture, causing uneven stresses between early and late wood; this causes cracking, cupping, splitting, etc.

Prolonged high moisture content provides excellent environment for moss, mildew and fungus growth

Wood goes through wet/dry cycles

Ideally, vertical wood surfaces should be properly prepared and finished within 3-5 weeks of installation completion

Ideally, horizontal wood surfaces should be properly prepared and finished within 2-4 weeks of installation completion

Finishing all six sides of all exterior lumber is hugely advantageous for providing optimum wood protection from the weather elements

Illustrations of Excessive Weather Exposures

The Nature Of Wood

• Cellulosic fibers- Lignin holds fibers together

• Extractives- Tannins give wood its color

• Water

• Pressure-treated lumber- CCA or ACQ- High moisture content- Mill Glaze

• Cedar-Red Cedar-Redwood- High extractive content- Mill glaze- Cedar is naturally oily

• Tropical Hardwood- Hard- Dense- Oily

Excess Moisture Content –When wood like pressure treated CCA (Chromated Copper Arsenate) or ACQ (Alkaline Copper Quaternary) are delivered to the job site it has a moisture content that is in excess of 40%.

Rapid drying can cause undo stress to the wood fibers that can lead to cracking, warping and cupping etc...

New Wood Can Present Several Problems

The Nature of Wood

New Wood Can Present Several ProblemsMill Glaze – is a term used by the coating industry to define what occurs on

smooth flat grained wood during the milling (wood planer) process.

● Natural oils come to the surface with machining heat

● The wood pores are shut and the finish will not penetrate properly

New Wood Can Present Several Problems

Extractive Content - All wood contains water soluble chemical extractives which are deposited in wood cells as a tree grows.

● Aesthetic problems

● Wet/dry cycles increase extractive bleeding and nail staining

Nail Staining –not always rust from the nail

Extractive Staining

Weathering of New Wood: The Negatives

Ultraviolet light radiation “burns” the wood

● Loosening the wood fibers

- Color is lost and the wood turns gray

● Erodes the wood surface

־ Opens up the wood grain

- Occurs faster in the early wood than in late wood creating a washboard effect

- Wood retains more moisture, promotinggrowth of moss, mildew and fungus

Excess moisture leaves the wood so oils can penetrate

Grain opens up so oils are absorbed more deeply

Extractives are washed away evenly so that appearance is greatly improved

Weathering of New Wood: The Positives“Short-term” weathering of new wood can minimize these problems. Finishes will look better and protect the wood longer.

Mildew Menace

Illustrations of Aged and/or Previously Finished & Weathered Exterior Wood Surfaces(Refinish or Restoration Required)

Why Stain?

A properly applied finish protects against● Wood destroying fungus- Brown Rot- Dry Rot- White Rot ● Wood- Mildew- Sap Stain● Mold● Algae

Optimum conditions for fungus growthTemperature

● 75-85ºF

Moisture Content● <20% no activity● 20-30% activity increases● >30% encourages fungus growth

Dry Rot

Wood Mildew Infestation

Various illustrations of performing proper surface preparation of all exterior wood surfaces, insuring that surfaces are Clean & Porous (surface absorbency) before applying any type of a finishing material.

Surface Preparation Methods

Factory Pre-Stain Applications

Factory Pre-Stain Applications

• Controlled application conditions

• Controlled substrate

• Stained or finished 6 sides

• Consistency – machine applied

• Low cost effective

• Year round install and done!

Factory Pre-Stain Applications

• Finish paint warranties

– 15 or 25 years on primed

• Certified Applicators

• Machine Coaters in all regions

Factory Pre-Stain Applications

Project Site Applications

Project Illustrations

• Western Red Cedar Lumber Association (WRCLA)

- “How to Specify Western Red Cedar” Brochure Link:

http://www.realcedar.com/wp-content/uploads/2015/03/76370_HowToSpecifyCedar_text_english_2015.pdf

- “How to Finish Western Red Cedar” Brochure Link:

http://www.realcedar.com/wp-content/uploads/2013/12/HowToFinish_english.pdf

- “Growth Properties and Uses of Western Red Cedar” Brochure Link:

http://www.realcedar.com/wp-content/uploads/2013/12/Growth-Properties_2013.pdf

Resource References #1

• Western Red Cedar Lumber Association (WRCLA)

- “Western Red Cedar Quick-Facts” Brochure Link:

http://www.realcedar.com/wp-content/uploads/2013/06/WRC-Quick-Facts.pdf

• Paint Quality Institute (PQI)

- “Difference Between Paint and Stain” Article Link:

http://www.paintquality.com/en/advice-and-tips/faq/exterior/difference-between-paint-and-stain

Resource References #2

• Journal of Architectural Coatings (Design+Durability Publication)

- “What Works Well With Wood” Article Link:

http://www.durabilityanddesign.com/archive/?fuseaction=view&articleid=3384

• U.S. Forest Products Laboratory (USFPL)

- “Durability of Paint or Solid-Color Stain Applied to Pre-Weathered Wood”

Publication Link:

http://www.fpl.fs.fed.us/documnts/pdf1993/willi93b.pdf

Resource References #3

• U.S. Forest Products Laboratory (USFPL)

- “Solid-Color Stains on Western Red Cedar and Redwood Siding”

Finish Line Publication Link:

http://www.fpl.fs.fed.us/documnts/finlines/finishline_mknaebe_2013_010.pdf

- “Paint, Stain, Varnish, or Preservative ?” Finish Line Publication Link:

http://www.fpl.fs.fed.us/documnts/finlines/finishline_mknaebe_2013_014.pdf

Resource References #4

• Cedar Shake & Shingle Bureau

- Western Red Cedar Sidewall Finishes / Coatings Options Brochure Link:

http://www.cedarbureau.org/cms-assets/documents/4902-639103.finishes-coatings-web.pdf

Resource References #5

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