Basswood blinds and slats Specification: What Each Number Actually Changes

The datasheet for basswood blinds and slats lists six or eight numbers, and most buyers compare the first one. That is the mistake this page is about: the numbers interact, and the one you ignore is usually the one that produces the claim.

Why the headline number is the least useful one

Every quotation leads with slat width. It is easy to compare and it is the number the factory can hit most cheaply. But it tells you almost nothing on its own: slat width sets the frame, and the parameters below set whether the product survives its first year in service. A buyer who compares only the headline figure is buying a sample, not a supply agreement.

For basswood, the practical rule is to fix the headline figure at the level your product needs and then spend your negotiating attention on moisture content and species. Those two are where cheap goods differ from adequate goods, and they are usually absent from the quotation sheet.

The numbers that decide performance

Read the table as a set of trade-offs rather than a checklist. Moving any single line usually costs money somewhere else, and the cheapest way to hit one figure is often to let another slip.

Slat width

Typical range: 25 / 35 / 50 / 63 mm. The visual decision. 50 mm is the volume seller; 63 mm reads as premium.

Slat thickness

Typical range: 2.3-3.2 mm. Stiffness and cord-hole strength. Under 2.5 mm, long slats sag.

Moisture content

Typical range: 8-12 %. The single most important number. Outside this range, warping is a matter of time.

Species

Typical range: Tilia (basswood). Straight grain, closed pores, takes lacquer evenly.

Grain and defects

Typical range: vertical grain, no knots, no blue stain. Cosmetic grade drives yield and therefore price.

How to write a basswood specification that protects you

A specification is only useful if a substitution becomes visible. That means writing the construction and the performance together, and naming the test that proves each one. For basswood, the clause has to pin moisture content and species, because those two separate a compliant lot from an adequate one:

Basswood venetian blind, 50 mm slat, 2.8 mm thickness, moisture content 8-12 %, vertical grain no knots, 3-coat water-based lacquer, warp <= 1.5 mm/m, cordless with tension device to EN 13120, stain 3A

Note what is missing from that line: adjectives. No ‘high quality’, no ‘premium’, no ‘export grade’. Every clause is either a number with a tolerance or a named test. If a supplier cannot quote against a line written this way, that is information about the supplier.

Where the specification usually breaks down

The first failure is warping and bowing. Slats curve within weeks of installation, worst near windows and in heated rooms. The cause is usually moisture content outside 8-12 %, or slats packed before equalising. The test that exposes it before you order: Moisture meter on 10 slats per carton plus a 48 h conditioning test at 23 C / 50 % RH.

The second is colour mismatch between slats. One blind looks striped because slats came from different stain batches. It comes from stain bath drift and mixing slats from two production days. Test with Visual under D65 on an assembled blind, plus dE <= 1.5 against the approved standard. and write the result into the purchase order, not just the enquiry.

Both failures share a pattern: they appear months after delivery, they are hard to attribute, and the cost lands on the buyer rather than the mill. That is exactly why the test belongs in the specification and the report belongs in the shipment file.

What to put in a basswood enquiry

1. End use and the conditions, which together decide where moisture content has to sit inside 8-12 %.
2. The one figure that must hold, with moisture content named as the proof.
3. Quantity per colour and per delivery, against a typical MOQ of 300-500 sets per colour.
4. Destination market, because compliance changes the construction, not just the paperwork.
5. A physical standard viewed under a stated light source, not a screen proof.

With those five points we can quote against a real requirement instead of a generic range. Full ranges sit on the basswood page, and the manufacturing side of the same question is on our quality control page.

Questions buyers ask before ordering

What moisture content should I specify?

8-12 %. Below 8 % the slat takes up moisture and cups; above 12 % it shrinks and bows. Ask for the meter reading on the shipped carton, not the kiln record alone.

Is 2.5 mm thick enough for a 50 mm slat?

For widths under 1.8 m, yes. Above that we recommend 2.8 mm, and above 2.4 m we reinforce the cord holes.

Do you supply cordless?

Yes, with a tension device tested to EN 13120. For the US we also supply to 16 CFR 1120, which is a different and stricter requirement.

Failure modes worth a clause in the purchase order

Claims rarely come from a batch that was obviously wrong. They come from a slat width figure that sat inside the quoted band and outside what the product needed.

The other two, with acceptance numbers attached, are in the full failure analysis for basswood. A supplier who cannot name the mode he sees most often is describing a catalogue, not a process.

Seven lines that turn a quotation into a specification

Most post-delivery arguments are not about quality. They are about a document that never said which figure would be measured, on which instrument, at whose cost.

1. Slat thickness: the figure you will accept inside the 2.3-3.2 mm band, the tolerance on it, and the method used to measure it.
2. Moisture content (8-12 %): name the number, not the word. If the answer only repeats the band, ask which point inside it is being offered for this order.
3. Species: Tilia (basswood) is the market band. Fix the figure you will test at goods-in, and the instrument you will test it with.
4. Grain and defects (vertical grain, no knots, no blue stain): fix the value per shipment, and state who pays for the re-test if a lot lands outside it.
5. Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
6. Packing and marking: shipping mark, roll or carton count and the tolerance on quantity, since a short shipment is a claim too.
7. Who inspects: third-party, in-house or none, decided in advance, with the AQL level written down.

Related reading

• Species in Basswood blinds and slats
• What Basswood Really Costs
• Basswood for Residential refurbishment