After removing old mastic (silicone), how do I clean the surface before applying the new seal?

Question

Also, is it possible to mastic over old mastic, or will it not adhere
properly. Both questions apply to my shower enclosure, which
I am re-tiling. The join is that which connects the shower tray
to the tiles on the wall.
Thanks in advance.
Matthew

Answer 1

you can get a mastic solvent, screwfix web site, sealants and adhesives, sealants, three products at bottom of page. good chance you can get it in B&Q also
If your enclosure is glass and tiles not plastic try green scotch brite and soap to remove the last of the old mastic.
I have put a new bottom in a glass fish tank and not redone the vertical joints, and it is still holding after 5 years, but that was with high modulus silicone sealant not the low modulus sealant sold for bathrooms.

Answer 2

1

Answer 3

I'm a plumber & carpenter
first use good quality silicone sealent, not the cheeper sealents that have little silicone.
if the old mastic is not visable when the final silicone is in palce, then use a stanley knife to cut out the old silicone. Where its is visable then carefully useknife or any scrap of timber to rub off the old silicone. Its conna take time though.
All loose material is vacumed out. If the walls are not so sound use a paint brush and paint on a wall sealent (pva with water 50/50) and wait for it to dry
Its very importaint that the seal is full with silicone and sticks to the wall and shower tray. Play extra attention to the corners of the tray.
I see bad diy jobs that have failed almost every day. Any water leaking through can get expensive if left unseen (wet rot etc)

Answer 4

I would use a razor blade, or craft knife.
the job MUST be dry and dust free,
finish the grouting let it dry completely
use a silicone that has a high modulus and fungicide
i would try and remove all the old mastic, it makes for a better looking job, just take your time,
Don't cut the nozzle to far back , Thin beads are easier to work with, wet your index finger and pull across the bead this pushes the mastic into the joint. (polish the tiles to remove any residual grout) b4 applying grout.

Answer 5

How To Remove Mastic

Answer 6

Don't use the seal strip its rubbish in an area that gets as wet as your shower tray. Use the silicon remover (from B&Q or similiar) wipe off any dirt/grease with a rag dipped in white spirit - make sure you wear gloves as it is an irritant and you must leave the rag to dry out before throwing it away as they can spontaneously combust. Then all you have to do is apply new sealant try and make sure it has a mould inhibitor as this area does go mouldy quickly.

Answer 7

Do not add new sealant over old. You can buy plastic putty knives at Walmart or Discount Stores. These will not scratch the surfaces. I use denatured alcohol to help remove it and clean the area afterwards because it removes oil and soap residue. Tip: A spoon dipped in water makes a great tool for smoothing the new silicone.

Answer 8

I was just about to ask this question myself, but you have done it for me. I'm re-doing the sealant around my bath & have removed most of the old silicone, but there are still some yucky bits. I don't think it will adhere properly if it isn't totally clean... anyway, I'll watch your answers now... best of luck with the job.

Answer 9

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Answer 10

There is a silican solvent remover, which you may find at somewere like B&Q, I'm sure its only a paint thinner, not white spirit or turps. Scrape most of it off with a stanley knife, and finally go back to a clean surface before resealing again. That stuff that smells like pear drops it will remove it as well
probably thinking off nail varnish remover