Removing old silicone without leaving residue
Old silicone is removed in two steps: first cut the joint bead out at a shallow angle with a cutter or joint scraper, then dissolve the residues on both flanks with a surface cleaner such as OTTO Cleaner F. Only when the substrate feels rough and no shiny spots remain will new silicone adhere permanently.
Contents
What you need
Project template “Renew the silicone joint in the bathroom”You remove old silicone without leaving residue in two steps: first work the bead of sealant out mechanically with a cutter or joint scraper held at a shallow angle, then dissolve the remaining residue on both flanks free of grease with a surface cleaner such as OTTO Cleaner F. Only when the substrate feels grippy and no shiny spots can be seen any more will new silicone adhere permanently. Anyone who only wipes off the surface risks the new joint coming away again after a short time.
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Why does silicone residue stay behind so stubbornly?
Silicone is designed to stay permanently elastic – and it is precisely this property that makes removing it completely difficult. Instead of coming away like a rigid coating, the bead tears into small shreds as you pull and leaves a thin film on the surface. The most common reasons why residue is still left afterwards:
Silicone tears into pieces when pulled off
The elasticity prevents the whole bead from being removed in one pull. Small remains stay behind above all in the corners and at the back of the joint.
Thin silicone film on porous substrates
On tile joints, natural stone or unglazed ceramic, a wafer-thin silicone film draws into the surface that is hardly recognisable with the naked eye.
Mixed with grease and soap residue
In the sanitary area in particular, old silicone combines with soap and limescale residue into a sticky layer that can hardly be dissolved completely by mechanical means alone.
Hardened remains in hard-to-reach corners
In internal corners and at silicone transitions to taps, old material sits particularly firmly because there is less surface for the cutter to attack.
How to remove old silicone step by step
New silicone only adheres permanently to a really clean substrate free of grease. That is why the double effort of mechanical removal and chemical after-cleaning is worthwhile:
| Step | What to do | Check |
|---|---|---|
| 1. Loosen the bead roughly | Place a cutter or joint scraper at a shallow angle (not vertically) and pull the silicone bead out in pieces as long as possible from one flank to the other. Vertical pressure scratches tile glaze and acrylic bathtubs. | Back of the joint is clear, only thin remains still visible on the flanks |
| 2. Loosen the residue on the flanks | Carefully scrape off the remaining crumbs and shreds with the blade, guiding it flat rather than scratching. Work particularly gently on natural stone and acrylic, as scratches stay visible. | No silicone crumbs left to feel or see |
| 3. Degrease the substrate | Wipe both flanks with OTTO Cleaner F surface cleaner and a clean, lint-free cloth. The cleaner dries quickly and without residue; according to the data sheet no flash-off is necessary. | Substrate feels free of grease and grippy, no shiny spots visible any more |
| 4. Dry test | Wipe over once more with a dry cloth to pick up the last moisture and dissolved residue before the joint is remade. | Cloth stays clean, no discolouration or residue left on the cloth |
| 5. Reseal | Seal again with OTTOSEAL S100 – an acetoxy-curing 1K silicone sealant to DIN 18545 part 2 group E, with fungicidal and bacteriostatic additives. Application temperature +5 °C to +35 °C. | Even, bubble-free bead of sealant |
| 6. Tool the joint | Tool it in one pass with smoothing agent and the OTTO Fugenfux Multi silicone smoother before a skin forms. | Smooth, closed surface with no air pockets |
| 7. Let it cure | Let the joint cure right through before it gets wet or is put under load. | Scratch test: the surface feels firm and can no longer be pressed in |
You will find complete instructions for resealing in our How to: replace sanitary silicone – step by step.
How not to damage the substrate
Guide the cutter flat, not vertically
Always place the blade flat against the flank. Vertical pressure leaves scratches in tile glaze and acrylic bathtubs that can no longer be removed.
Work particularly carefully on natural stone
Polished natural stone surfaces show every scratch permanently. Work with little pressure here and test at an inconspicuous spot before you remove over a wide area.
No sharp metal scrapers on plastic
On acrylic bathtubs and plastic shower trays, metal scrapers quickly leave visible grooves. Use a plastic cutter at a shallow angle of attack instead.
Never just apply over the residue
New silicone does not adhere permanently to old, cured material. The old joint always has to be removed completely and the substrate cleaned.
Common mistakes – and how to avoid them
Only wiped off the surface
If only the visible bead is removed, a thin film stays behind on which new silicone does not hold permanently. Always follow up with cleaner as well.
Overlooking corners and transitions
It is in internal corners and at tap transitions that residue most often stays behind. Check these spots individually and deliberately.
Using tools that are too aggressive
Sharp metal tools or unsuitable solvents can permanently damage tile glaze, acrylic or natural stone. Always match tool and cleaner to the substrate.
Resealed too early
If the cleaner has not dried off completely, the new silicone cannot adhere optimally. Before sealing, briefly check whether the surface is really dry.
Frequently asked questions
What is the best way to remove old silicone without leaving residue?
First work the bead of sealant out mechanically with a cutter or joint scraper held at a shallow angle, then dissolve the remaining residue on both flanks free of grease and without residue with a surface cleaner such as OTTO Cleaner F.
Can I simply apply new silicone over old residue?
No. New silicone does not adhere permanently to old, cured silicone or silicone residue. The substrate has to be cleaned and degreased completely before the joint is remade.
What do I clean the substrate with after removing the old joint?
With a surface cleaner such as OTTO Cleaner F. It removes grease and silicone residue, dries quickly and, according to the data sheet, leaves no residue of its own.
How do I know there is no silicone residue left?
By touch and visual inspection: the substrate has to feel grippy and free of grease, with no shiny or sticky spots. A clean cloth that you wipe over it with must no longer pick up any residue.
Can I use a metal scraper on acrylic bathtubs or tiles?
On plastic surfaces such as acrylic bathtubs you should not use sharp metal scrapers, as they leave visible grooves. Use a cutter at a shallow angle of attack and with little pressure. On glazed tiles a metal scraper is possible with care; on natural stone you should do without it entirely.
How long does the cleaner have to flash off before I reseal?
According to the data sheet, no separate flash-off is necessary with OTTO Cleaner F, as it dries quickly and without residue. Before sealing, still check briefly by hand that the surface is completely dry.
If your new joint keeps cracking open despite clean preparation, read the Guide: Silicone joint keeps cracking – causes and solution. For choosing the right colour and product in the wet area, the Guide: Which silicone for the shower? helps. You will also find suitable products directly in our category sanitary silicone.
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