How to fix yellowed No More Gaps?

Question

Hi team

A few years ago I redid the laundry in our apartment with a lot of help from the staff on this forum.

Unfortunately a few months after all of the caulk on the skirting and around the cabinets yellowed, remained sticky and attracted dust that can't be removed.

I'm going to have to re do the whole lot but wanted to know what went wrong?

Attached is a pic. I used sellys no more gaps in white.

EricL · Answer

Hello @dchur

Some of the reasons that silicone turns yellow are oxidation, UV exposure, heat, or exposure to cleaning chemicals. Other common causes include mould/mildew in damp areas, chemical reactions (e.g., mixing different types of sealants), or the aging of lower-quality non-UV-resistant products.

How do I make sure I don't make the same mistakes that caused this?

I can only propose the following steps:

* Get a good high quality UV resistant silicone that has mould and mildew resistance.
* Remove all the old silicone on the surface so that there will be no mixing of products.
* Use masking tape to limit the spread of the silicone so that the bead will be small and precise. 
* Make sure to avoid using chemical cleaning products on the surface of the silicone so that there will be no chemical reaction.
* If you have blinds or curtains, make sure to cover your cabinets so that it is not exposed to heavy UV rays.

If you need further assistance, please let us know.

Eric

dchur · Answer

Thanks Jacob.

On further inspection and comparing it to other sealents around the apartment I believe i actually used silicone, not 'no more gaps' on these surfaces. it feels the same and isn't as "chalky" as the no more gaps.

given that silicone isn't meant to be painted, i wonder why this has happened on it? I'm going to have to re-seal it all, but how do i make sure i don't make the same mistakes that caused this?

The laundry doesn't get humid, we don't have a dryer. and the windows are always open for air circulation.

JacobZ · Answer

Hi @dchur,

Most acrylic gap fillers like this are designed with the expectation that they will be painted once they have cured. Paint acts as a protective layer that seals the surface of the filler.

Without that protective layer, the surface can remain slightly porous or rubbery. This makes it easier for dust and grime to stick to the surface over time, which can make the caulk look dirty and feel tacky even if it has technically cured.

Standard interior gap fillers can also yellow if they are left exposed, particularly in areas with heat and humidity. A laundry environment can accelerate this because of moisture in the air and heat from appliances such as dryers. Over time this combination can lead to the yellowing and dust buildup that you are seeing now.

So, it seems likely that the filler itself did cure, but because it was left unpainted and exposed to a warm, humid environment, the surface gradually attracted dust and discoloured. When you redo it, a quick coat of paint can help to reduce the stickiness and prevent the discoloration over time.

Let me know if you have any further questions.

Jacob