Where Do The Yellow Spots On uPVC Frames Come From?

Where do the yellow spots on uPVC frames come from?

The cause of the yellow spots on plastic windows were initially metal dusts of unclear origin.

Here are some amazing facts!


In 2003, yellow spots appeared on white plastic windows in Austria & Switzerland for the first time. Investigations by independent institutes showed a change in the surface due to a chemical reaction, which was due to deposits of metal dust.

Gradually, this phenomenon, coming from the south, also spread over Germany. Where these dusts came from was at first puzzling.
Was suspected that metal abrasions or metal dust, which could come from brake discs.
Also suspected were emissions from industrial areas or railroad tracks, which also cause metal scrap when the trains brake.

Rust on stainless steel railings was already well known. The oxidation of an iron dust, which comes to rest on a PVC profile, under the influence of UV light chemical destruction of the PVC surface, which leads by means of metal decomposition, pollen and UV light to a yellow discoloration around the metal point but was new.

Oxidizing metal chip surrounded by a yellow yard; for comparison of sizes to the left of a ballpoint pen tip.

When direct UV light is involved, the yellow discoloration on the south side of the houses is logical & understandable.
However, why a single house is often affected by this phenomenon in a development area has long remained unanswered.

What the lawn fertilizer has to do with uPVC windows?

It was only when a technician in the uPVC industry came up with the idea to help his newly planted lawn with lawn fertilizer & bought a "ferrous lawn fertilizer" in a garden centre, suddenly came a logical explanation:
In the generous distribution of iron-containing lawn fertilizer metal dusts.
These are the reasons why a single house in a residential area is often affected - the windows in the lower floors are intensified there.

If the metal dusts are not removed by washing in the following days, they may settle - mainly in the lower profiles - & cause the problems described above.


Yellow discoloration without iron dust

Danger detected, danger averted. So you might think so, but far from it. The yellow discoloration by iron dust followed a few years later another problem: The large-scale yellow discoloration of the white plastic profiles without the action of iron dust with a frequently accompanying line-shaped elevation on the PVC profile.

And here is the cause of the cleaning process: The new generation of household cleaners & detergents is noticeable by the fact that the bottle size is getting smaller & smaller & the concentrations of cleaning agents are getting bigger & bigger.
These cleaners therefore call themselves "concentrates".

Whereas in the past, a strong dose of washing-up liquid was added to an undefined amount of water, on the reverse side of these means you will now find dosing instructions that could come from a pharmaceutical laboratory to their accuracy. For many cleaning concentrates, the dosage is approximately as follows: Use 3ml of cleaning concentrate per 5 litres of water. In German 3 drops of the concentrate to 5 litres of water.

If these cleaners contain additives such as orange, lemon or peppermint flavour, it will be exciting because these acidic substances can attack the PVC surface.

If ammonia and / or benzyl alcohol are found in the cleaning agents, destruction of the PVC surface in the micro range is almost to be expected!

These substances are not to be found in a uPVC cleaner.
Especially Benzyl alcohol oxidizes with oxygen to Benzaldehyde which according to the chemistry with hard uPVC is now completely incompatible.


Too much cleaner, too much concentration

If you now use a powerful spray instead of 3 ml of cleaning concentrate & mix it with only approx. 2 litres of water instead of 5 litres, you will overdose by a factor of 25 to 30.
The chemical cleaning additives are thus overdosed by 25 to 30 times,

The additive lactic acid is by its very nature harmless, but in a strong overdose lactic acid is extremely aggressive towards uPVC.
In France and Spain, there is a chlorine bleach to buy in the super market, which can be used in very small doses to disinfect drinking water. Used in excessively high doses when cleaning the floor, it can be used to generate chlorine fumes, which make any toxic gas cloud appear as a mild spring fragrance during the First World War.

If the opened window sash is cleaned with overdosed ammonia-containing cleaners and then closed, the chemical substances were enclosed between the sash profile and the frame stop seal and can now react with the uPVC.
Small swelling on the wing profile is the result.
Due to the sealing system, these swellings are as straight as if they had been pulled with the ruler.

These surveys are usually in time before the yellow discoloration & are a clear indication of the abuse or overdose of household cleaners.
At least one advantage at a disadvantage: It saves you the labour costs.
The discussion with the end customer remains.

Cleaning the surfaces

Since this problem is caused by the misuse / overdose of household cleaners or in response to iron dust, it goes without saying that the yellow stains cannot be removed with household cleaners. The professionals say.

Only by sanding the surface or by abrasive cleaning of the profiles can the affected windows be cleaned.

Only by sanding the surface or by abrasive cleaning of the profiles can the affected windows be cleaned.
Following the sealing of the treated surface.
Then the profiles are clean again.
Of course, a clear warning from the builders must not be missing, not to clean the windows again with the budget funds; otherwise the problem starts all over again!

As a prevention should already be made when submitting the offer the indication that the cleaning of the uPVC surfaces may be done only with an agent that is free of flavours, serpentines, ammonia or benzyl alcohol, or is best carried out with a cleaner, which the window supplier provides you.

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