The benefit of colour-matching using a non-silicone sealant comes if you need to paint over it (such as spray-painting the side of a bus). A non-silicone sealant will not repel the paint meaning it will not flake off and crack.
Can You Paint Over Silicone Sealant?
You may think that painting over existing silicone sealant would be a quick way of tidying sealed joints around windows, skirtings etc. However, you will quickly discover that this is not such a good idea.
Should you attempt to paint over silicone, you will come across two main issues:
- The paint will have a thin, streaky finish, no matter how many coats you apply.
- The paint will eventually flake, leaving a patchy mess. This is especially common in areas that are regularly cleaned, such as interior window frames etc.
So now you know that paint will not stick to silicone, let’s take a look at why .
Why does paint not stick to silicone sealant?
This may sound like a simplistic answer, but silicone is designed so that nothing will stick to it. With its waterproof characteristics and extremely smooth finish, the paint will not adhere well enough for it to last. This is especially true in areas that are cleaned or wiped down on a regular basis.
Lightly wiping a painted silicone bead with a damp cloth will only remove the paint.
Silicone will also stretch and contract, sometimes up to 25% of its original size. As paint does not share the same flexible characteristics, it is sure to crack and flake in areas of relatively high movement.
Can you make silicone paintable?
Many DIY bloggers will try to give away “trade secrets” and claim there are ways you can make paint stick to silicone. But unfortunately, for reasons mentioned previously, these simple tricks and hacks do not work in the long term.
Can you caulk over silicone sealant?
Decorators caulk is a great substitute for silicone in areas where waterproofing and excessive movement is not an issue (ceiling perimeters, skirtings, architraves etc). Applying caulk in these areas is a great way of filling gaps and taking your eye away from insightly joints, plus you can paint over it.
So can’t you just caulk over silicone?
The sealant you’re using will determine how difficult painting over will be
You won’t find it difficult to paint over all sealants. You may be thinking sealant and silicone are the same things. They aren’t.
There are several different types of sealants. As the name suggests, a sealant is any type of adhesive that is used to ‘seal’ a gap or void.
Silicone is one type of adhesive. When people say to use a ‘silicone’, they likely mean to use a sealant. Sealants can be made up of one of several chemistries; Silicone, hybrid polymers (like MS polymers) and polyurethanes to name a few.
You will not find it difficult to paint over sealants with a base chemistry of hybrid (MS) polymer or polyurethane.
On the other hand, you will find it very difficult (pretty much impossible) to paint over silicone. So for the purpose of this article, we will explain why you cannot paint over silicone.
Why is painting over silicone so difficult?
This section is where we could get technical. But, we have tried to simplify the answer as much as possible.
To begin with, we should explain that silicone and emulsion paints aren’t compatible. If you paint over the top of silicone with emulsion paint, the silicone will repel the paint.
The main reason for this is the hydrophobic nature of silicones. As Emulsion paint is water-based, the silicone will repel the paint.
The ability of silicone to repel water & form watertight seals is the main reason it such an effective sealant and is why it is so popular.
As mentioned already, this is a very top line demonstration of why water and silicone don’t bond. But hopefully, it makes it a little clearer.
How can you paint over silicone?
Now that you have an idea behind the reason why you will struggle to paint over silicone, we will discuss some options that could help you paint over it. We aren’t saying they will work though.
The first option you can try is to use oil-based paint. These use solvents which take the place of the water in emulsion paints. This means the silicone will not repel the paint – but it doesn’t necessarily mean that it will attach to it.
You have to bear in mind that some paints and silicones will contain budget-grade raw materials. These low-quality materials could be in place of other additives that improve adherence. Yet we know that oil-based paints are not always a viable option.
If you have tried oil-based paint and it doesn’t work or you can’t use oil-based paint, there is still one other solution you can consider:
Try etching the silicone with sandpaper to give more surface area for the paint to stick.
This method is commonly used when trying to find a way around the problem.
Here at Forgeway, whenever we get asked for methods to paint over silicone we always say that you shouldn’t be in this situation in the first place. You shouldn’t need to worry about paint cracking or flaking off after it has covered the sealant.
Several options are available to eliminate the need to paint over silicone, but you will need to plan ahead to ensure they work.
