Buyers argue about slat width more than about any other figure in PVC slats, and they usually argue about the wrong part of it: the number itself rather than the tolerance behind it.
What slat width actually controls in PVC slats
50 mm dominates; 25 mm is for small windows and bathrooms.
That makes it a design decision rather than a purchasing one, which is why changing it after the product is fixed costs more than changing the material.
For PVC blinds and slats, the working range is 25 / 35 / 50 mm. Inside that band the choice is commercial; outside it, the product changes category and so does the price.
How to choose a slat width option
| Option | What it changes in PVC slats | When it is the right choice |
|---|---|---|
| 25 | The lowest-cost option in the family. Yellowing is where it usually ends up. | Cost-led programmes with a short service life |
| 35 | The volume middle: enough margin for process variation without paying for headroom the end product cannot use. | Most repeat programmes, and the safest default |
| 50 mm | The top of the family, where the process is controlled tightly enough to guarantee it. | A warranty, a tender, or a specification that cannot be renegotiated |
These are alternatives, not points on a scale. Slat width is chosen by the application rather than by price, and a supplier who quotes one option as if it were interchangeable with another is quoting a different product.
Buyers default to the floor because it is the cheapest compliant answer. That is rational until the first claim, and then the saving is measured against a replacement shipment.
The figure that decides the outcome is not slat width itself but the tolerance around it. A supplier who quotes 25 / 35 / 50 mm without a tolerance has not quoted a specification, and the first lot will define the tolerance for you.
How to measure slat width
The reference method here is Yellowing, run to QUV 300 h, with an acceptance of dE <= 3. The method is the easy part; sampling and conditioning are where reports diverge.
Measure on the goods as delivered, not on the greige or the pre-finished material. The figure that matters is the one in the product your customer receives.
Record the measured value rather than pass or fail. A marginal pass on slat width tells you the process is running at the edge, which is the information you need before the next lot rather than after it.
Slat width does not stand alone
Slat width moves with thickness (1.8-2.5 mm) and with uv stabiliser (required, stated in phr). Tightening one usually costs money in another, and a supplier who accepts every tolerance without comment has either not understood the interaction or is planning to substitute.
When you change slat width, re-check the two neighbours before you approve the sample. Most of the samples we re-make are caused by a change in one figure that was not followed through.
The clause to write for slat width
The line below is the version we can quote against without inventing anything. Slat width appears with a tolerance and a test, not as a standalone number.
PVC venetian blind, 50 mm slat, 2.0 mm wall, UV stabilised, QUV 300 h dE <= 3, HDT >= 65 C, co-extruded woodgrain, cordless to EN 13120
The clause that protects you is not the value, it is the sentence that says what happens when the value is missed. Put it in the purchase order, not only in the enquiry.
When slat width goes wrong
Yellowing. White slats turn cream within a year in a sunny window.
The cause is usually insufficient or wrong uv stabiliser; often tio2 grade rather than a true uv package.
The test that catches it: QUV 300 h, measure dE and yellowing index.
What to specify instead: Specify the stabiliser system and require the QUV report; do not accept ‘UV treated’.
The pattern is consistent: the failure appears months after delivery, is hard to attribute, and the cost lands on the buyer. That is the argument for measuring slat width on every lot rather than on the development sample.
Four questions about slat width, before you order
- What tolerance do you hold on slat width, and what did your last three lots measure against it?
- Which method do you use for yellowing, and which laboratory signs the report?
- When slat width falls outside 25 / 35 / 50 mm, do you rework, downgrade, or ship and hope?
- Which of thickness or uv stabiliser would you move first to hit a lower price?
The answers are more useful than a certificate, because they show whether the process is controlled or merely inspected. Full ranges for PVC slats are on the product page, and the measurement regime is described on the quality control page.
Questions buyers ask before ordering
Will white PVC yellow in a sunny window?
Not if it is properly stabilised. Ask for a QUV 300 h report with dE <= 3. Without that report, assume it will yellow.
Is PVC allowed in the EU?
Yes for window coverings, but the compound must comply with REACH and heavy-metal limits, and some buyers restrict PVC on brand policy grounds. We supply both and will tell you which is more common in your market.
Three questions, and the answers that separate mills
If the PVC slats figures on this page is going to be decided on a call, take these three questions into it.
| Question | Answer that should worry you | Answer that holds up |
|---|---|---|
| Which test catches cold brittleness? | “We have never had a complaint.” | Impact at low temperature — on the production lot, with the acceptance figure written into the report and not into the email. |
| May I see a report for a lot you shipped last month? | “That is confidential customer information.” | A redacted report, which carries every number that matters and none of the customer’s identity. |
| Where in the available to EN 13501 B-s1 band will this order sit? | “In the middle, normally.” | A stated target and the readings behind it. Fire performance drifting inside the band is how a conforming lot still fails. |
Failure modes, and the test that catches each one
A specification only earns its keep if it names the failure it prevents. These are the two that matter for the PVC slats figures on this page.
| Failure | What triggers it | Test to demand on the production lot |
|---|---|---|
| Woodgrain film peeling | Laminated film without adequate primer or edge sealing. | Colour fastness to light — ISO 105-B02; acceptance >= grade 4 |
| Yellowing | Insufficient or wrong UV stabiliser; often TiO2 grade rather than a true UV package. | Fire performance — EN 13501-1; acceptance B-s1,d0 where specified |
The other two, with acceptance numbers attached, are in the full failure analysis for PVC slats. A supplier who cannot name the mode he sees most often is describing a catalogue, not a process.
Need slat width specified and tested against your end use?
Send a window schedule or a single set size and we will return a quotation with the loading plan, the safety standard that applies to your market and the lead time for the colour you need. Catalogue and current price list on request.
Related reading
- Pvc Slats for Commercial kitchens and labs
- Yellowing resistance in PVC blinds and slats
- What Pvc Slats Really Costs
Catalogue and current price list · Neutral packing and private label · Consolidation, documents and lead times
