Choosing an Effect Paint Primer: Proper Surface Preparation

Short answer: An effect paint primer is chosen according to the type of surface that will sit under the effect paint. According to the silkcoat.com product pages, Silkcoat Izolac is used on absorbent surfaces and surfaces levelled with gypsum plaster, Silkcoat Universal Primer on old, dirty or solvent-based (synthetic) painted surfaces, and Silkcoat Putty Primer on surfaces finished with putty. Before priming, the surface is cleaned of dust, dirt and grease, and any defects are levelled with putty.

What is an effect paint primer?

An effect paint primer is a preparation coat applied to the surface in a single coat before the effect paint. It balances the absorbency of the surface and helps the effect paint adhere well. The primer acts as a bridge between the substrate and the effect paint: if an absorbent gypsum surface quickly draws the water out of the paint, the effect will not spread evenly; if a water-based product is applied directly over solvent-based paint, adhesion is weak.

The effect paint pages on silkcoat.com list priming as a separate step. The instruction on the Metalico page is clear: once the primer has dried, two coats of Metalico are applied to the surface. The Marmarito, Velvetto and Pearl pages also state which Silkcoat primer to use for each type of surface. That is why choosing the primer for an effect paint is as important a decision as choosing the product itself.

Which primer for which surface?

According to the Silkcoat product pages, the choice of primer depends on the condition of the surface: gypsum and absorbent, old or solvent-based painted, or finished with putty. The recommended primer for each surface type is summarised in the table below:

Surface condition	Recommended Silkcoat primer	What the primer does (silkcoat.com)
Absorbent, dusting surface levelled with gypsum plaster	Silkcoat Izolac	Prevents the gypsum surface from absorbing the paint, so the paint bonds with the surface
Old, dirty or solvent-based painted surface	Silkcoat Universal Primer	Makes it possible to apply water-based products over solvent-based paint
Interior surface finished with putty	Silkcoat Putty Primer	Increases the hiding power of the topcoat and helps it adhere well to the surface

On silkcoat.com, Silkcoat Izolac is described as a transparent interior primer for gypsum and absorbent surfaces. Silkcoat Universal Primer is an acrylic copolymer-based primer developed for applying water-based paint over solvent-based paint. Silkcoat Putty Primer is described as a primer that creates a surface ready for the topcoat after interior putty work; on the Marmarito page the same product is listed as Silkcoat Putty Astar. All three primers are in the interior paints and primers category.

How is the surface prepared before priming?

Before priming, the surface is cleaned of all dust, dirt and grease, blistered and previously painted areas are lightly sanded, and defects are repaired with Silkcoat interior acrylic putty. The surface preparation steps given on the silkcoat.com effect paint pages are as follows:

1. Cleaning: The surface is cleaned of all dust, dirt and grease. According to the Marmarito page, swollen and old paint is scraped off.
2. Sanding: All blistered and previously painted surfaces are lightly sanded; the aim is a clean, dry and sound surface.
3. Putty: If the surface is uneven or cracked, a smooth surface is achieved with Silkcoat interior acrylic putty.
4. Extra sanding on glossy surfaces: On very glossy, glass-like surfaces, the surface is sanded first to create a sound base for better adhesion.
5. Inspection: After putty and sanding, the surface is checked under raking light; we cover this step in our article on checking effect paint for defects with raking light.
6. Primer: The Silkcoat primer suited to the surface is applied in a single coat, and the effect paint goes on once it has dried.

According to the technical data on silkcoat.com, Silkcoat interior acrylic putty is applied at a consumption of 500-1500 g/m² depending on the surface and dries in 1-4 hours depending on weather conditions. During application and drying of the putty, the ambient and surface temperature should be between +5ºC and +30ºC.

What are the technical values of Silkcoat primers?

According to the technical data on silkcoat.com, Silkcoat Izolac covers 25 m²/lt in a single coat, while Silkcoat Universal Primer and Silkcoat Putty Primer cover 10-15 m²/lt in a single coat; all three are fully dry in 24 hours. The values listed on the pages of the three primers are:

Value	Silkcoat Izolac	Silkcoat Universal Primer	Silkcoat Putty Primer
Consumption	Single coat 25 m²/lt	Single coat 10-15 m²/lt	Single coat 10-15 m²/lt
Touch dry	15-20 min	15-20 min	15-20 min
Dust free	1 hour	1 hour	1 hour
Fully dry	24 hours	24 hours	24 hours
Application temperature	+5ºC to +35ºC	+5ºC to +35ºC	+5ºC to +35ºC

According to the instructions on silkcoat.com, Silkcoat Izolac is diluted with clean water at a 1:2 ratio before application. Silkcoat Universal Primer and Silkcoat Putty Primer are thinned with clean water and applied in a single coat by roller, brush or spray; for the dilution ratio, refer to the technical data sheet on the product page. According to silkcoat.com, Universal Primer can be stored for at least 2 years in its unopened packaging in a cool, clean and dry place.

How does the primer recommendation vary between effect paints?

Most Silkcoat effect paint pages follow the same three-part rule: Izolac on gypsum or absorbent surfaces, Universal Primer on old painted surfaces, Putty Primer on puttied surfaces. There are small differences from product to product:

Effect paint	Primer instruction on the page
Marmarito	Universal Primer on smooth, previously painted surfaces; Putty Primer on puttied surfaces; Izolac for smooth, glossy surfaces
Velvetto	Izolac on surfaces levelled with gypsum plaster; Universal Primer on old, dirty or solvent-based painted surfaces; Putty Primer on puttied surfaces
Pearl	Izolac on new and absorbent surfaces; Universal Primer on old, dirty or solvent-based painted surfaces; Putty Primer on puttied surfaces
Metalico	Izolac on surfaces levelled with gypsum plaster; Universal Primer on even, old, dirty or solvent-based painted surfaces; Putty Primer on puttied surfaces

The Travertino page does not name a specific primer; it states that the product can be applied to all prepared, painted interior surfaces and that defects and cracks should be repaired with Silkcoat interior acrylic putty. You can find the steps for a marble-look finish in our article on how to apply marble effect paint.

When can primer and effect paint go on a newly plastered wall?

According to the Pearl and Izolac pages on silkcoat.com, you should wait at least 28 days before painting newly plastered surfaces. During this period the new plaster loses its moisture; primer and effect paint applied too early may not adhere properly to the surface.

Conditions on the day of application are checked too. For Silkcoat primers and for effect paints such as Marmarito, Velvetto, Pearl and Metalico, the ambient and surface temperature should be between +5ºC and +35ºC throughout application and drying. The primer takes 24 hours to dry fully; according to the instructions on the Metalico page, the effect paint is applied once the primer has dried.

Conclusion

• An effect paint primer is chosen according to the surface: Silkcoat Izolac on gypsum and absorbent surfaces, Silkcoat Universal Primer on old, dirty or solvent-based painted surfaces, Silkcoat Putty Primer on puttied surfaces.
• Before priming, the surface is cleaned, blistered paint is sanded, defects are levelled with Silkcoat interior acrylic putty and the surface is checked under raking light.
• Wait at least 28 days on new plaster; primer and effect paint are applied between +5ºC and +35ºC, and the effect paint goes on once the primer has dried.
• To choose the right primer for your surface together, get in touch with us; you can browse all our effect paints on the effect paints page.