How to prepare a support with flaming?

Among the techniques for preparing surfaces for painting, flaming is a sufficiently well-known technique which can provide unique and extremely effective solutions in a number of applications ranging from car paints to bottle, flask or plastic paints.

Tutorial for flaming before painting

Flamming improves adhesion on certain materials that are difficult to adhere to, and on the other hand it allows better wetting of liquids on the smooth surface (plastics, glasses, etc.).

Here is a summary tutorial for practicing flaming on plastic

Step 1 ► Remove adhesives, paint residue, dirt...

If there are stickers on the surface of the plastic, they must be removed. Using hot air softens the glue and makes peeling easier. Expose the plastic by sanding or cleaning. It is also possible to prepare the plastic (by rubbing with an abrasive sponge and thinner).

Step 2 ► Degrease with anti-silicone cleaner

It is important to remove any glue, silicone or grease residue before flaming. Using a professional degreaser also helps reduce surface electrical tension and produce an antistatic effect.

Step 3 ► Flame the surface

With a flame powered by gas projected with a torch:
Make 2 back and forths on the surface of the plastic. The flame should lick the “plastic”. The torch should always be moving and should not linger on the plastic. The temperature of the plastic must not rise above 70°C, in order to avoid any deformation of the plastic. Depending on the thickness of the plastic, the applicator can judge the number of passes the plastic can withstand without deformation.
The flame should preferably be blue. The yellow flame is a sign of poor combustion and produces black residue. To remedy this, simply clean the combustion residue from the torch tip.

Step 4 ► Painting

When passing the flame over the plastic, we can immediately observe a sweating phenomenon. After the flame has passed, the gloss level of the plastic may be lowered. Flaming removes all surface tension. This allows the paints to spread better on contact with the surface of the plastic, but also to adhere more effectively to these surfaces which are generally difficult to hang. This is a so-called “covalent” atomic level bond. After flaming, the painter has a time window of approximately 10 to 30 minutes to take advantage of the absence of surface tension.
→ Apply a plastic primer

What do we call flaming?
Flaming is not a blowtorch because this flame is too concentrated and too hot to be used on materials by flaming, we designate the use of a flame which results from propane or butane by a shaped torch type burner. round or triangular.

You don't get the same effect with a heat gun that projects hot air.

It is practiced with caution given the nature of the support, with a few quick passes over the surface.

The action of flaming on car paint.
The flame in contact with the surface has the particularity of making the “surface tension” disappear: Surface tension is an electrical tension present on certain materials. In particular, it creates a problem for wetting and the proper distribution of liquids on the surface, in the form of a “dropping effect” or “refusal” on the surface. Flaming also allows adhesion to the support through the phenomenon of covalent bonding: it is an approach to the support without the help of additives or primers.
The duration of the effectiveness of the action of flaming on the surface is up to 30-60min.

Practical applications of flaming
We carry out flaming, for example, on plastics in the bodywork sector. Some plastics are very difficult to adhere and flaming is an essential step; this is also recommended by the biggest automotive paint brands for the treatment of polypropylene and polyethylene. Flamming provides excellent adhesion of paints to plastics by allowing the plastic to open and release certain solvents.

Painting on glass
All glass painting specialists do flaming before painting or priming: Both on glass and ceramics, it is an effective way to disperse liquids well and to obtain adhesion.
This is practiced in particular by specialists in the decoration of perfume bottles in the field of bottling.
On glass, it is of course essential to apply either an adhesion primer for glass and ceramics, or a direct adhesion varnish on glass.
For manufacturers, there are also more innovative surface treatment solutions with vacuum plasma (Corona effect).

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