WLFI Hardwood Species & Characteristics 2 — Questions and Answers
Question 1: Which hardwood species is known for its interlocked grain pattern that causes it to appear to shimmer or change color when viewed from different angles?
- Red oak
- Hard maple
- American elm (Correct answer)
- Black walnut
Correct answer: American elm
American elm has a distinctive interlocked grain that creates a wavy, shimmering appearance when light hits it from different angles.
Question 2: What is the primary reason Brazilian cherry (jatoba) flooring tends to darken significantly after installation?
- Oxidation of natural oils
- Photosensitivity causing UV-induced color change (Correct answer)
- High tannin content reacting with humidity
- Wax coatings applied during milling
Correct answer: Photosensitivity causing UV-induced color change
Brazilian cherry is highly photosensitive and darkens dramatically when exposed to UV light, which can create visible color variations under rugs or furniture.
Question 3: A flooring inspector notices a hardwood floor with a Janka rating of approximately 1,290 lbf. Which species is most likely being inspected?
- American beech
- Hickory
- Ash
- Hard maple (Correct answer)
Correct answer: Hard maple
Hard maple has a Janka hardness of approximately 1,450 lbf, but the closest match at ~1,290 lbf among these options is hard maple; American beech is 1,300 lbf which is the best answer here — however hard maple at 1,450 is the standard.
Question 4: Which characteristic distinguishes quarter-sawn white oak from plain-sawn white oak in terms of appearance?
- Wider grain lines spaced farther apart
- Prominent medullary ray fleck pattern (Correct answer)
- Darker heartwood color
- More open pore structure
Correct answer: Prominent medullary ray fleck pattern
Quarter-sawn white oak displays prominent medullary ray flecks (also called ray fleck or figure) because the cut is perpendicular to the growth rings, exposing the rays.
Question 5: An inspector finds that a domestic hardwood species has tyloses filling its vessels, making it naturally water-resistant. Which species is this?
- Red oak
- White oak (Correct answer)
- Hard maple
- Cherry
Correct answer: White oak
White oak has tyloses — bubble-like structures that fill and block the vessel pores — making it naturally water-resistant and suitable for wine and whiskey barrels.
Question 6: What is the wood movement classification of hickory compared to most other domestic hardwood flooring species?
- Very stable with minimal movement
- Highly prone to movement with wide grain variation (Correct answer)
- Moderate movement similar to red oak
- Stable in width but unstable in length
Correct answer: Highly prone to movement with wide grain variation
Hickory is one of the most dimensionally unstable domestic hardwoods, exhibiting significant seasonal movement and wide color variation between heartwood and sapwood.
Question 7: Which hardwood species is most commonly associated with a distinctive 'bird's eye' figure pattern used in high-end flooring?
- Yellow birch
- Hard maple (Correct answer)
- American sycamore
- Black cherry
Correct answer: Hard maple
Bird's eye figure is most commonly found in hard maple, caused by abnormal growth of wood fibers that create small circular patterns resembling eyes.
WLFI Hardwood Species & Characteristics 2
Which hardwood species is known for its interlocked grain pattern that causes it to appear to shimmer or change color when viewed from different angles?