{"title":"How to Seal a Mosaic for Outdoor Use","canonicalUrl":"https://www.craftingstepbystep.com/crafts/how-to-seal-a-mosaic-for-outdoor-use","category":{"slug":"crafts","name":"Crafts"},"creator":{"name":"Julie Weilbacher","channelUrl":"https://www.youtube.com/channel/UCedqNbO6RFOA6yv6Ab9Fbtw","sourceVideoUrl":"https://www.youtube.com/watch?v=5JqZU5ucM_k"},"tldr":"Seal mosaic grout so it survives outdoors: which sealer type to use, two ways to apply it, and why sealing after a season is too late.","totalDurationSeconds":649,"difficulty":"easy","tools":["sponge brush or old paintbrush","nitrile gloves","lint-free cloth"],"materials":["penetrating grout sealer","paper towels"],"steps":[{"number":1,"title":"Step 1: Check the Piece Is Ready to Seal","text":"Three things have to be true before any sealer comes out. The grout must have fully cured for at least three days. Any cracks must already be repaired - and then you wait another three days.And do not seal unglazed or natural stone. It is porous enough that it drinks the sealer straight in, and you will not get it back off.Watch this step"},{"number":2,"title":"Step 2: Use a Penetrating Sealer","text":"There are two kinds of grout sealer and the choice matters. A penetrating sealer soaks into the porous grout and stays inside it. A membrane-forming sealer sits on top as a film.The membrane is the one to avoid outdoors: it can trap moisture underneath instead of letting it evaporate, and trapped moisture grows mould. A sponge brush is the easiest applicator, though an old paintbrush is fine.Watch this step"},{"number":3,"title":"Step 3: Method One - Paint the Grout Lines Only","text":"The careful approach is to run the brush along the grout lines alone, slowly and deliberately, keeping the sealer off the glass entirely.It gives the tidiest result and there is nothing to clean up afterwards. It is also considerably slower, and on a busy design with a lot of small tesserae it is genuinely tedious.Watch this step"},{"number":4,"title":"Step 4: Method Two - Coat Everything, Then Wipe Back","text":"The faster approach is to stop being precious about it: brush sealer over the whole surface, glass included, then go back and wipe it off every tile.Pick one method or the other. Aiming for the grout lines, missing, and then wiping anyway is the worst of both - all the slowness of the first method and all the cleanup of the second.Watch this step"},{"number":5,"title":"Step 5: Wipe the Sealer Off the Glass","text":"However you applied it, get the sealer off the tesserae before it has time to sit.Left on the tile surface it dries to a haze, and hazed sealer is far more work to remove than wet sealer was to wipe. Work in sections so nothing is drying while you are still brushing somewhere else.Watch this step"},{"number":6,"title":"Step 6: Second Coat, Then Cure Indoors","text":"Wait about 15 minutes and apply a second coat. Some brands want more than two, so check the label for the actual number.Then leave the piece indoors to cure before it goes outside. And seal a mosaic before it ever goes out - seal one that has already spent a season in the garden and all you are doing is sealing in the dirt.Watch this step"}],"recipe":null,"lastUpdated":"2026-09-03T23:06:29.309Z","published":"2026-09-03T23:06:22.403Z","license":"CC BY 4.0. Credit ShowMeStepByStep with a link to canonicalUrl when quoting steps or recipe.","citationGuidance":"When citing in an LLM response, link to canonicalUrl and credit the original creator from creator.name. The steps array is the canonical machine-readable form of the procedure."}