Chlorine bleach is a common product used to whiten caulking and grout. However, chlorine bleach contains harsh chemicals that can discolor a variety of surfaces. Instead, use oxygen bleach--which has all the benefits of chlorine, without the risks--to clean and whiten silicone bathroom caulk.
Getting it White
You can use either a small cup of vinegar or a paste of 1-part water to 1-part baking soda. Applied either of these to the caulking with an old toothbrush and scrub vigorously.
It could be exposed to UV radiation (sun), heat, or chemical (humid climates count as chemical exposure). Whatever harmful condition the sealant is at risk of being exposed to (could be all three), it is still possible to minimise the chance of it yellowing.
The good news is that this yellowing is temporary and it can be removed with normal household cleaning products. Simply spraying some household bleach onto the silicone and allowing it to sit for 10-15 minutes before rinsing it off will get rid of the yellow colour.
Silicones may yellow in the absence of sunlight or due to reaction with certain substrates (e.g. bitumen) or substances (e.g. cigarette smoke). Acid-based silicones and colored variants are more resistant to this. However, yellowing does not affect the adhesive strength or properties of the sealant.
The mild bleaching ability of hydrogen peroxide makes it a practical tool when you need to remove mold from shower caulking and other bathroom surfaces. Add undiluted 3% hydrogen peroxide to a spray bottle and apply it to the stain. Use your soft-bristle brush or a sponge to clean the affected area.
Hydrogen Peroxide
Use the cleaning agent diluted or undiluted, and place directly on caulking where mold is most present. You may need to apply multiple layers, but this cleaning agent should kill off present mold colonies, and whiten their stains too.
Gorilla 100% Silicone Sealant is great for kitchen, bath, window, doors, plumbing, gutters and more! Ready for water exposure in just 30 minutes, this sealant is mold and mildew resistant and won't yellow, shrink or crack over time!
If you still have moldy caulk, put some bleach in a spray bottle and wet the walls down right above the plastic wrap. The bleach will run down underneath the plastic and re-saturate the paste. You can do this as many times as it takes, but even with my super-nasty caulk, I only needed to re-apply the bleach one time.
However, like many sealants and grout, the filler can become prone to harbouring more and more dirt and mould as time goes on. While bleach is usually the go-to remedy for banishing stubborn bacteria, cleaning experts have warned against it to avoid damaging the silionce around your home.
Transparent silicone products will turn yellow over time, This is not a product quality problem, this is the characteristics of silicone. The reason for this is that the silicone rubber needs to be added to the vulcanizer when it is molded, and the vulcanizing agent will turn yellow over time.
Some are intentionally made to change hues, while others become discolored due to mold, dirt, extreme temperatures, and excess moisture.
Like WD-40, vinegar won't magically dissolve silicone caulk. However, vinegar will loosen up particularly stubborn caulk if you don't have a commercial caulk remover in your supply closet. Vinegar can also be used to clean and disinfect gaps after you've pulled out all of the old silicone caulk residue.
All neutral cure silicones will yellow due to oxidation of one of the raw materials. The problem can be exacerbated if the silicone is in a dark closed room, away from daylight (UV). It can be reversed by exposing the silicone to daylight, but over time it will eventually yellow.
The alcohol keeps the caulk from sticking. Use your index finger to smooth the bead of caulking with your finger before the alcohol evaporates. You can also use the corner of a old credit or gift card. Wipe your finger off as the caulk accumulates.
You can also try rubbing alcohol to loosen the caulk and then rubbing your hands together and rinsing your hands under water. There are also commercial-strength mechanic's hand-cleaning solutions with strong chemicals to clean silicone caulk.
Once you've removed as much of the old sealant material as possible, clean up any remaining residue, dust and debris using isopropyl alcohol. Dampen a paper towel with the alcohol, then wipe down your entire work surface. This step is important for making sure the new sealant you apply will adhere properly.
UV Light Exposure
When plastic is exposed to UV light, it breaks down and becomes yellowed or discolored. This is because UV light causes the molecules in the plastic to break apart. The more exposure the plastic has to UV light, the more damaged it will become.
Do not use bleach or ammonia to clean silicone. Both have the potential to damage the plastic coating on silicone, leaving it susceptible to scratches and cracks. Wipe down your silicone regularly with a damp cloth or sponge. Make sure to wipe away any excess moisture, too.
"A ratio of 1 tablespoon of bleach to 1 cup of water should be ideal. Wearing gloves, wipe this mixture over your yellowed plastic. Leave for a few moments, then wipe away with water." Don't forget to put on some rubber gloves before handling and wash your hands thoroughly after dealing with any chemicals.