Odd streaks on paint surface

Depending on the depth of the streaks I would sand and fill then repaint after priming

This is usually caused by painting directly onto new plaster without a proper mist coat, which highlights trowel marks and uneven suction. It’s fixable by lightly sanding, sealing the wall correctly, and repainting. Happy to take care of it and get it looking perfect.

Uneven distribution of paint applied maybe due to cheap sleeve or irregular pressure with roller

What you are seeing sounds like “plaster scratches” or surface streaking”, which can happen if the plaster wasn’t fully dry before painting or if it was sanded unevenly. Other causes can include:
• Applying paint too early on new plaster (moisture still in the wall)
• Poor surface preparation, e.g., not sealing or priming the plaster properly
• Using a low-quality brush or roller that leaves marks

To fix:
1. Lightly sand the streaked areas to smooth the surface.
2. Apply a mist coat (diluted emulsion) to seal the plaster if it hasn’t been primed.
3. Repaint with 2 proper coats of quality emulsion, using even strokes.

Make sure the plaster is fully dry (often 1–2 weeks for new plaster in UK conditions) before repainting, and avoid painting over damp or powdery surfaces.

New plaster is very absorbent and needs a layer of two of what's called a mist coat to seal it before being able to apply emulsion. In and ideal world you would use a product first such as Supermatt from Dulux which is designed for new plaster or alternatively a standard emulsion diluted by up to 40% and applied with a roller or spray system as your mist coats.

During the final troweling stage, the plasterer may have worked the plaster too much, creating a smooth, glassy, and non-porous surface. The paint cannot stick to this, causing it to streak, run, or create strange patterns.

The newly plastered wall joint filler was probably still not dry when the wall was painted and as it dried it has now cracked.

Light sand area use filler with scraper . Dry sand go over with emulsion 2 coats preferably

streaks appeared. These streaks look like deep, knife-like lines, almost as if someone had scratched the wall with a Stanley knife. In reality, though, it’s usually not actual damage. It’s more likely due to the way the plaster was finished and how the paint interacts with it. Essentially, the plaster’s surface was uneven, and once the paint dried, those differences became visible.

This is almost certainly trowel marks / plaster polishing showing through the paint, not damage done after painting.

On newly plastered walls, if the plasterer has over-trowelled or polished the surface, it creates areas of different density and suction. When you apply paint, those differences show up as streaks or lines that can look like knife marks.

What you’re seeing is a very common paint-on-new-plaster issue, and it’s almost never knife damage.

These fine, linear streaks are caused by uneven suction from the new plaster, sometimes combined with trowel marks that only reveal themselves once painted.

There can be many issues, first you need to identify the cause of streaks either it is due to efflorescence or due to the plaster not fully cured yet or there might be some contamination. First you fix the problem then prepare the surface with a primer and then applying good quality paint in even coats.
Solution is If plaster not cured, give it time to dry completely and use a de-humidifier to speed up. If efflorescence is the problem then brush off and use efflorescence treatment solution to neutralise salts.

Those strange streaks on your newly plastered, painted wall are likely due to surfactant leaching (from high humidity/moisture interfering with paint drying), uneven paint application/porosity, or possibly salt deposits from the plaster/damp, not a Stanley knife; you'll need to properly clean and repaint, maybe with a specialized paint or a better mist coat on the plaster first, and ensure good ventilation.

The wall should have been sealed with one or two mist coats of 50/50 paint and water prior to emulsioning the final colour, this prevents the new plaster sucking the moisture from the paint and cracking/streaking

Maybe bad plasterer edge of trowel marks sand down and apply watered coat first then top coat again maybe whole wall

Strange streaks on newly plastered walls—especially ones that look like fine cuts or drag marks—are usually caused by salts, poor plaster drying, or trowel marks coming through the paint rather than anything you’ve done wrong.

When plaster dries too quickly, or if the plasterer over-trowelled the surface, it can leave fine “shiny lines” that only appear once paint has gone on. In other cases, salt deposits or uneven suction in the plaster can cause the paint to dry in streaks that look like scratches.

The best fix is to lightly sand the affected area, apply a stain-blocking or adhesion primer (Zinsser Gardz or BIN are ideal), and then repaint. If the lines are physical rather than visual, a thin skim of filler to level the surface before priming will give you a perfect finish.

It could be PVA streaks caused by excess PVA used by the plasterer. Without more info it's difficult to ascertain the cause. Try using a stainblock and then repainting.

Thank you for your message.
The streaks you’re describing often happen when new plaster wasn’t fully sealed or dried before painting. If the wall wasn’t mist-coated (a watered-down first coat of emulsion) or if moisture is still coming through the plaster, the paint can dry unevenly, leaving marks that look like scratches or knife lines.

Here’s what I’d recommend:

Lightly sand the affected area to smooth it out.

Apply a stain-blocking primer or sealer (such as Zinsser or Dulux Trade Stain Block).

Repaint with two thin coats of your chosen emulsion.

If the streaks reappear, it may be due to damp or salts coming through the plaster (called efflorescence) — in that case, it’s worth checking for hidden moisture before repainting.

Those streaks are most likely due to the plaster not being fully cured before painting, or the paint drying too quickly on the surface. When that happens, the paint film can pull unevenly and create lines or cracks that look like scratches. The best fix is to sand down the affected area lightly, apply a mist coat or primer sealer, and then repaint with a roller using even strokes. Make sure the wall is completely dry before painting again — ideally, freshly plastered walls should dry for at least a week or more depending on thickness and ventilation.

If the plaster was even slightly damp when painted, moisture can get trapped beneath the paint film.

As it dries, it causes tension and hairline cracking, often showing up as streaks or sharp lines (which can look like scratches or knife marks).

You should always put a primer on new plaster ( mist coat ) after that a base coat then a top coat. This should be fine, unless of course the new plaster needs sanding down.

If the plaster wasn’t completely dry before painting — even if it looked dry — moisture trapped underneath the paint film can cause fine “crazing” or knife-like fissures as the plaster continues to shrink.
You’ll often see:

Thin, straight or jagged hairline cracks.

Sometimes darker streaks following those lines (moisture tracking through).

Sand down surface, then wash down with sugar soap, allow to dry, then put on a miss coat of paint, 30% paint 70%water, dries in 15-20 minutes, then de-nib meaning lightly rub down, wash with water, the apply another coat 50% paint 50% water, allow to dry then lightly rub down, wash the surface with water, allow to dry then add final coat 100 %paint.

Possible Causes
1. Incomplete plaster curing/drying – If the plaster still had moisture when you painted, salts can migrate to the surface and leave streaks (efflorescence).
2. Poor sealing/priming – New plaster should be sealed with a mist coat or plaster primer. Without it, paint can soak unevenly, creating streaks or scratches.
3. Application issue – If paint was applied too thinly, or if rollers/brushes were dragging, it can leave “knife-cut” like lines.
4. Surface contamination – Dust, jointing compound residues, or leftover adhesive can telegraph through paint once dry.
5. Movement in plaster – Hairline cracks from drying shrinkage sometimes look like scratches.

Sand lightly, clean if salty, seal with primer/mist coat, then repaint.

The "streaks" on your new, plastered and painted wall are likely not from a Stanley knife, but from paint bloom or salt migration, which are white marks caused by moisture in the plaster or walls affecting the paint. Other causes could include physical damage during plaster curing, dust and residue from inadequate surface preparation, or even moisture trapped in the plaster.

Would have to be sanded down a bit and filled with painters mate before repainting

The plaster may not be fully dry and causing lines when painted not 100% dry. You would normally wait a wk.

You will need to get the wall back to the surface by using a fine sandpaper ensuring that its smooth and gets rid of the streaks, bringing it back to the plaster will ensure that any thing you put on top will be smooth. Test if the walls are ready by applying a test patch of paint, look out to make sure its adheres and dries evenly. Apply a proper mist coat this will help bond the new surface to the paint, allow to try and fully. Then the walls should be ready to apply new paint.

If it's like scratches in the wall then best thing would be to use a wall filler and rub down using 120 grit sandpaper before repainting

Hi, prevoius paint not keyed to plaster, suspect no base primer added

1. Plaster not fully dry:
Even if it felt dry, plaster can take days (sometimes weeks) to fully cure. Painting over damp plaster can cause weird streaks, cracks, or even peeling later.
2. No mist coat applied:
Fresh plaster is very porous. If you didn’t apply a mist coat (usually watered-down emulsion, about 70% paint, 30% water), the plaster may have sucked the moisture out of the topcoat, causing streaks, patchiness, or cracking.
3. Surface contamination:
Grease, dust, or sanding residue on the wall can also lead to strange lines or marks after painting.
4. Paint incompatibility or poor adhesion:
If the topcoat paint is thick, high-sheen, or of low quality, it may not adhere well to plaster and instead exaggerate surface imperfections like trowel marks or scratches.
5. Hairline cracks or crazing in the plaster:
What looks like “knife lines” could actually be fine hairline cracks in the plaster itself—especially if it was applied too thick or dried unevenly.

can happen with couple of reasons.
inadequate preparation, too cheap paint, painting techniques,
maybe using the same roller after leftover overnight.
some times humidity of the room.
Can be sorted with a spounge and water.
May need more preparation and sanding
might be help with a primer

We need to sanding ..filling..again sanding then paint

This could be due to painting over plaster that wasn’t fully dry or skipping the mist coat, which helps paint stick properly to new plaster. Dust or poor surface prep can also cause streaks, and drying plaster can sometimes shrink and crack.

To fix it, lightly sand the area, fill any damage, and make sure the wall is clean and dry. Apply a mist coat if it wasn’t done before, then repaint. A primer-sealer may help if the issue returns.

This could be due to the plaster not being fully dry before painting, or no mist coat/ primer was applied. Fresh plaster needs time to cure and should always be sealed first. The streaks might also be from poor paint adhesion or physical damage. Lightly sand the area, apply a proper primer, and repaint for a smooth finish.

Most likely there is no scrim tape under the multifinish.

There are a few possible reasons for those streaks. If the newly plastered wall wasn’t fully dried or primed properly before painting, the paint may not have adhered correctly, causing lines or cracks to appear over time. Sometimes, leftover plaster dust or a lack of mist coat (diluted first coat) can lead to similar issues. To fix it, I’d recommend lightly sanding the affected area, applying a suitable primer or sealer, and then repainting. It’s important to let fresh plaster fully cure—usually 5 to 7 days—before painting to avoid problems like this

Sometimes, the plasterer’s trowel leaves fine lines or ridges that only become obvious after painting.

If the plaster was not completely dry before painting, or if a mist coat (a diluted first coat of paint) was skipped or poorly applied, paint can absorb unevenly. perhaps paint shrinking due to uneven drying, absorbtion or even due to the contamination from the substrate...

Sometimes, PVA adhesive (used to seal old walls before plastering) can splash onto the surface or be used excessively. If not properly absorbed or if it dries on the surface, it can prevent paint from sticking, causing streaks, spots, or marks

1. Insufficiently Sealed or Primed Plaster

New plaster is very porous and needs to be properly sealed before painting. If not, the paint can dry unevenly, soak in too fast, or highlight imperfections. This often results in streaks or patchy textures that look like scratches or knife marks.

Solution: If the wall wasn’t mist coated (a diluted emulsion used as a primer) or properly primed, the topcoat won’t adhere properly. You may need to:
• Sand back the affected areas.
• Apply a proper mist coat or plaster primer.
• Repaint with a high-quality emulsion.