A Common Reno Problem: Is It Oil or Water Based Paint On Your Old Timber Trims?
How to Tell if Your Old Aussie Timber Trims & Doors Were Painted with Oil-Based or Water-Based Paint Decades Ago.
Ah, the joys of repainting old timber trims, architraves & internal doors. It’s the quintessential Aussie home improvement task – you grab a tin of paint, a trusty paint brush & set off to give those tired old surfaces a facelift. But hold on friends, not all paints are created equal. Before you go slapping on a fresh coat, you need to figure out what paint was originally used. Is it oil-based or water-based paint? This mightn’t seem like an important question but let me assure you, it is. Paint over a surface with the wrong type of paint and you could have a peeling paint disaster to deal with in the very foreseeable future.
As much as I like to think I’m a bit of a paint expert, a few weeks ago, I found myself pondering this very question as I stared at the back of an internal door on my latest renovation. It had turned a kind of off-whitish-slight-yellowish tinge over time. You know the look — that slightly grotty shade of “old rental property beige.” It got me thinking: was this an oil-based paint job gone slightly yellow or was it just my eyes playing tricks on me? And more importantly, what would happen if I painted water-based paint straight over it?
The old door on my latest reno throwing off white, yellow tinges.
OIL-BASED VS WATER-BASED PAINT: THE LOWDOWN
First, let’s talk about what sets these two paints apart:
- Oil-Based Paint: Back in the day, oil-based paints were the go-to for all your timber trims, architraves & doors. This paint was tough as nails, durable & gave a high glossy finish. The downside? Over time, oil-based paint tends to yellow (especially on white or lighter colours) and can have a bit of a pong – you know, that strong, solvent smell that makes you feel like you’re doing something serious.
- Water-Based Paint: These paints on the other hand, are the modern darlings of the painting world. They dry faster, clean up easily with water (no turps needed, hallelujah!), and don’t have that nose-tingling smell. Plus, they stay true to their colour over time — no weird yellowing.
HOW TO TELL WHAT’S ON YOUR TIMBER?
So, how do you figure out what type of paint you’re dealing with? Here are a few easy tests you can do to help crack the case:
- The Alcohol Test
This one’s a beauty. Grab some methylated spirits (Metho) & a clean rag. Give the surface in question, a quick wipe. If the paint comes off onto the rag, it’s water-based. If it doesn’t budge, you’re dealing with oil-based paint. Super simple, huh? - The Yellowing Test
Remember that door I mentioned earlier? The yellowish tinge was my first clue it was oil-based paint. Water-based paint doesn’t yellow over time, but oil-based paint loves to pull this sneaky trick, especially in areas that don’t get much sunlight. - The Texture Test
Run your hand over the painted surface. Oil-based paint tends to feel smoother & harder, like glass. Water-based paint on the other hand, has a softer, slightly more rubbery feel. - The Scratch Test
If you’re brave (or the paint job’s already shoddy), use a coin to gently scratch the surface. Oil-based paint is tougher & much harder to scratch, while water-based paint comes off a lot easier.
WHY DOES THIS MATTER?
Now, this isn’t just a matter of paint snobbery. Knowing whether the existing paint is oil or water-based is critical when it comes to repainting. Here’s why:
- Oil Over Water: Painting oil-based paint over water-based paint is a big no-no. The oil paint won’t properly bond to the water-based layer & you’ll end up with cracking, peeling paint. Probably a bit of swearing too in the weeks or months following your DIY efforts.
- Water Over Oil: This is equally risky. Water-based paint doesn’t stick well to an oil-based surface unless you prep it properly. If you skip the prep, your lovely new paint job could start peeling off pretty quickly too.
SO, WHAT’S THE SOLUTION?
If you’ve convinced your existing paint is oil-based, here’s what you need to do to repaint your old trims, the right way:
- Prep is Key
Sand the surface thoroughly to rough it up & remove any signs of gloss. This gives your new paint something to stick to. - Prime Time
This step is non-negotiable. If you want to keep all your existing trims (previously painted in oil-based paint) but want to paint them in water-based paint and never deal with yellow tinges again, apply a good quality water-based undercoat over the old oil-based paint. The undercoat will act as a bridge / buffer between the two, making sure they play nicely together. - Choose Your Paint Wisely
Once you’ve applied one coat of undercoat, you can then go ahead & use 2 coats of water-based door & trim paint for a fresh, modern finish. If you want to stick with oil-based paint (maybe for durability in high-traffic areas), there’s no need to apply undercoat again, but sanding is still a must.
A QUICK WORD ABOUT LEAD-BASED PAINT
Before you go sanding or scraping all those old trims & doors to figure out if your paint is oil or water-based, don’t forget lead-based paint. If your home was built before the late 1970s, there’s a chance that lead-based paint is lurking beneath the layers.
Lead paint, when disturbed, can release harmful dust & particles that are dangerous to inhale or ingest (especially for kids & pets). Sanding, scraping or even aggressively cleaning a painted surface could expose you to this risk.
Here’s how to handle it safely:
- Use a lead test kit to check for lead in the paint layers.
- If you find lead, consider calling in a professional for removal or containment.
- If you’re determined to DIY, follow strict safety protocols: wear a P2 dust mask, use a sanding tool with a HEPA filter & avoid dry sanding.
Even if your focus is just figuring out whether the paint is oil or water-based, checking for lead first is a must. After all, you want to give your timber trims and doors a facelift — not endanger your health in the process!
Until next time,
Cherie Barber x
Common sense guidance! Thank you and look forward to more.
Thanks Yvonne. Cherie Crew x
What paint for a front entrance door?
Hi Helen, in line with todays decorating trends, I’d recommend painting your front door (external facing side) with an “external” water-based paint in either satin or semi-gloss finish. For the internal facing side of your front door, paint with an “indoor” water based paint in satin or semi-gloss finish. Both of these finishes are popular because they strike the right balance between aesthetics, durability & ease of maintenance. Happy painting! CB x
Hi Cherie,
What’s your opinion on using a deglosser over the oil paint, instead of sanding? I have just tried it over an enamel painted skirting board, on the recommendation of my painter. It’s too early to tell whether the top coat will peel over time, but am wondering if you’ve had any experience with this type of product, and whether in fact it is an alternative to sanding. I HATE sanding! Thanks Cherie.
Hi Dianne, yes deglosser is definately an alternative to sanding. In fact, it can be sometimes informally referred to as ‘liquid sandpaper’. Best to test the adhesion of your water-based paint after using deglosser by applying a small patch in an inconspicuous area. Allow it to dry fully and check if it sticks well without peeling. I personally havent used it but certainly know of it. CB x
dulux have an amazing paint primer that you put over oil base and then you can put the water base over it.. less prep and turns out great… i used it on my last project.
Hi Katrina, yes both Dulux and Taubmans have great undercoats / primers so either brand is fine. I would always recommend sanding still, even if its just a light sand. Reality is sanding is something we all hate doing! Thank you for reading our blogs. CB x