Based on the provided reference, using a water-based product over gloss paint is possible, but it depends specifically on the type of water-based product and requires crucial surface preparation.
Understanding the Reference
The reference clarifies that not all water-based primers are suitable for the same tasks. It makes a key distinction:
- Water-Based Undercoat: The reference indicates that water-based undercoat is suitable for use over oil-based gloss. It states, "One of the qualities of undercoat is superior adhesion, so using it on oil-based gloss isn't an issue providing you get the prep right." This highlights that products formulated as undercoats, possessing strong adhesion properties, can be applied over gloss paint, provided the surface is correctly prepared beforehand.
- Acrylic Primer: In contrast, the reference explicitly warns against confusing undercoat with acrylic primer, noting, "don't get your undercoat mixed up with acrylic primer, which is used on bare wood." This suggests that a standard water-based acrylic primer, typically designed for bare surfaces, is not the product recommended for application over existing gloss paint.
The Answer: It Depends on the Product and Preparation
Therefore, based on the reference:
Yes, you can use a water-based product specifically formulated for adhesion over existing paint, such as a water-based undercoat, over gloss paint.
No, you should not use a standard water-based acrylic primer (intended for bare wood) over gloss paint, according to the reference.
The critical factor is choosing a water-based product with sufficient adhesion qualities for a non-porous, potentially challenging surface like gloss, and then ensuring the surface is properly prepared.
Why Proper Preparation is Essential
The reference emphasizes getting the "prep right." While the reference doesn't detail the steps, proper preparation is universally required when painting over gloss to ensure any primer or undercoat adheres effectively. Key steps typically include:
- Cleaning: Thoroughly wash the gloss surface with a degreaser or appropriate cleaner to remove all dirt, grime, and grease.
- Sanding: Lightly sand (often called 'scuff sanding') the entire gloss surface. This dulls the shiny finish and creates a 'key' or texture that the primer/undercoat can grip onto, significantly improving adhesion.
- Dust Removal: Wipe down the sanded surface with a tack cloth or damp cloth to remove all sanding dust.
- Priming/Undercoating: Apply the suitable water-based undercoat or adhesion primer.
Summary Table
| Product Type | Suitability Over Gloss (Based on Reference) | Necessary Condition |
|---|---|---|
| Water-Based Undercoat | Yes | Proper surface prep |
| Acrylic Primer | No (Intended for bare wood) | N/A |
| Water-Based Adhesion Primer | Yes (If formulated like undercoat) | Proper surface prep |
Choosing the correct water-based product designed for adhesion over challenging surfaces like gloss, coupled with meticulous surface preparation, is the pathway to a successful paint finish.
