Dirty base
This is the most common and most costly mistake. A product applied to a dirty surface seals the dirt underneath, and the result is worse than if you had done nothing. On top of that, everything that got under the protective layer stays there for a long time.
The solution is simple. Always start with thorough cleaning, and difficult stains such as oil or rust you remove separately before you move on to impregnation.
Damp base
Water in the structure of the material stops the product reaching where it should and leads to streaks. A surface that looks dry on top is sometimes damp deep down, especially after rain.
Tip
When in doubt wait another day or two. Darker joints and hollows are a sign that there is still water in the material.
Wrong product
A product for indoor use will not cope with rain, and a penetrating impregnation will not sink into a sealed, painted surface. An equally common misunderstanding is expecting the wet look from an impregnation that is not meant to change the look at all.
So start with the question of where and why you are applying the product, then check in the product description whether it suits your use and your desired effect. More on the difference is in the guide on impregnation or coating.
Too thick a coat
More does not mean better. Excess product does not penetrate, it just gathers on the surface, forms sticky streaks and stains and dries longer. Better to apply two thin coats than one thick one, if the product allows it.
Skipping the test
A test on an inconspicuous spot takes a moment and saves many disappointments. It shows the colour, gloss and absorbency before you decide on the whole surface. With wet look coatings it is downright necessary, because it is hard to undo on the whole surface.
Wrong weather and time of day
Working just before rain ends with the fresh product being washed off, and in full heat the product evaporates before it can penetrate. Both lead to an uneven, weak result.
Note
Always check the forecast and keep to the temperature range on the label. Above freezing, dry and no rain during the drying time are the conditions that most often decide the success of the whole job.
Ignoring the label and product data sheet
Consumption, number of coats, drying time and use differ between products. Guides describe general rules, but the exact figures on the label and in the data sheet of the specific product are binding. Always read them before the work.
A short checklist before impregnation
- Surface clean, without deposits and stains.
- Surface dry, just below the top too.
- Product matched to the use and desired effect.
- Test done on an inconspicuous spot.
- Good weather, above freezing, without rain and heat.
- Label and product data sheet read.
Frequently asked questions
What to do if the impregnation left streaks?
Streaks are most often the result of too thick a coat or applying to a damp base. How to fix it depends on the product, so check the guidance in its data sheet. In future apply thinly and only to a dry surface.
Can a poorly done impregnation be corrected?
Usually yes, but how depends on the product and the surface. Sometimes a re cleaning and another thin coat is enough, sometimes the excess has to be removed. Start by checking the manufacturer guidance.
Why does water still soak in after impregnation?
The most common causes are applying to a dirty or damp base, too little product or the wrong product choice. It helps to return to the basics, that is cleaning, drying and a test before reapplying.
How many coats of impregnation should I apply?
It depends on the product and the absorbency of the surface. Absorbent and old bases often need two coats. The binding figure for the number of coats and the intervals is on the product label.
