When do I need to paint with Primers and Sealers in 2024?

Most people love colourful paints but the real stars are the primers and sealers, holding everything together and stopping the flashy top coats from emotional and physical collapse.

Primers and sealers ‘hang on’ to bare wood/Gyprock/brick/cement/plaster etc. AND THEN give top coat paint something to grip onto.

This is how a painted interior works:

1. There is a SUBSTRATE - A wooden door, a Gyprock ceiling, a brick wall, a plaster repair etc.
2. There is a TOP COAT (or ideally two top coats) - All the wonderful coloured paints that we see in the colour chips at Bunnings.
3. BUT … between them there needs to be sandwiched a layer of something: something that GRIPS the SUBSTRATE and also itself has a surface that the TOP COAT can grip to. This something is a PRIMER or a SEALER.*

*To complicate matters an old existing top coat can act as this gripping something if it is sound, but beneath it, and years of other top coats, there will eventually be a primer gripping to the original substrate.

* ALSO water based paint WON’T stick to old oil based paint.

Think of it this way. Any surface that doesn’t have sound, clean, existing paint needs some sort of primer or sealer before the tops coats go on. Without the right primer or sealer the top coat will start to peel.

Unfortunately cheap/bad painters often skip the priming stage because, hey its unseen! and the top coat just doesn’t last.

I’ve seen stair rails (water based paint over oil) fail within days and ceilings peel within months (ceiling paint over raw plaster).

So, what follows is a list of the primers that I have used and my opinions of them. It includes some that have a few drawbacks and some that I consider to be essential.

PRIMERS FOR TRIM
(WOODWORK - DOORS, WINDOWS, SKIRTING BOARDS, PICTURE RAILS ETC.)
Most existing or historic trim is painted with an oil based top coat. But most people now want a brighter, lower odour/VOC water based repaint.

PROBLEM! Water based paint does not stick to oil based paint. It just peels right off. I’ve had to fix numerous ‘water over oil’ stuff ups!

SOLUTION! Water based top coat paint WILL stick to an oil OR water based primer.
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Oil based primers - Clean up in turps

Dulux 1Step® Oil-Based Primer, Sealer & Undercoat is a fast-drying prepcoat suitable for the complete preparation of interior and exterior surfaces.

Sticks to everything but STINKS. I mean really bad chemical smell. It’s also oil based so you (or I) get the added fun of a smelly turps clean up.

This primer is old school and it works very well but here are modern alternatives that are much less smelly that stick just as well.
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Zinsser® Cover-Stain® Oil-Base Primer
Sticks as well as the Dulux 1Step and still smells but not nearly as bad. Also has the added advantage of blocking stains that soak through water based paints and primers.
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Zinsser® Odourless Oil-Base Stain Blocker
Just as good as Coverstain at gripping and stain blocking BUT has a lot less odour / VOC’s. To be clear this primer is not absolutely odourless but compared tho other oil based primers its ‘almost’ odourless. A huge improvement and still super effective.
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Water based primers- cleans up in water.

Dulux maximum strength adhesion primer
A fairly new primer that flows well and has a very clean white colour. Dulux makes some big claims about adhesion (stickiness) and for a water based primer its probably the best BUT … water based primers still don’t stick as well as oil based.

ZINSSER 1-2-3 Undercoat, Primer, Sealer
A good all purpose primer that leaves a very nice surface to paint over. But its still water based and … see above.

Sealers for raw substrates

Unpainted surfaces like Gyprock, plaster patching or repairs, old plaster walls and ceilings, brick or concrete walls need a sealer before a top coat can go on. Here are the sealers I use.

Zinsser Peel Stop
This is a white watery sealer that dries clear. I use it on ALL my plaster repairs and crack filling jobs after they dry. It’s very good. It dries quickly, washes out in water, and top coats stick to it. (I have cheated and used PVA glue also know as Bondcrete which looks the same. It works well but dries shiny and the top coats don’t stick very well, which sort of defeats the purpose!)
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Taubmans Tradex Ultra Prep White Undercoat
A good inexpensive sealer/primer that I put on new cement render repairs and new Gyprock. Taubmans claims it can do lots of other priming work but I prefer to use the other specialist products mentioned here.
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Specialist primers

Zinsser Interior and spot exterior primer - Shellac based, cleans up in Methylated Spirits
Super adhesive, BIN primer is the one for stubborn bleed through stains, nicotine stains, sap and weird timber bleed problems. I find it a bit hard to work with but not impossible. Also its alcohol based and the fumes can literally make your head spin. A specialist primer but great at what it does.
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DULUX METALSHIELD - Oil based, cleans up in turps
Metalshield is what needs to go on metal surfaces like metal gates, bars, railings etc. Its good for steel, aluminium, galvanised metal, even fibre glass. Pretty smelly but protects from bumps and knocks pretty well.

ZINSSER WATERTIGHT Mould & Mildew-Proof™* Waterproofing Paint - Oil based, cleans up in turps.
WATERTITE mixes oil based resin with portland cement! Its very thick and is best rolled rather than brushed on. It has mould killing properties and holds back a certain amount of moisture. I’ve use this on the OUTSIDE walls of bathrooms where leaks have soaked through. Sticks like crazy but a bit hard to use because its so darn thick.
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Dulux PRECISION Stain & Mould Blocker - Water based, Cleans up in water.
Dulux PRECISION Stain & Mould Blocker is designed to inhibit mould and mildew growth. I have a whole mould removal process and this primer is part of it. I’ve found it really helps to kill and prevent mould from returning.


So …

My favourite ‘stick to anything’, ‘low odour’, primer is Zinsser® Odourless Oil-Base Stain Blocker.
My favourite all purpose sealer is Zinsser Peel Stop.


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