How to Seal a Mosaic for Outdoor Use
Source: Julie Weilbacher • Full tutorial: www.craftingstepbystep.com/crafts/how-to-seal-a-mosaic-for-outdoor-use
- Difficulty
- Easy
- Hands-on time
- About 30 minutes
- Wait time
- 24 hours
- Cost
- About $10 to $18
Tools
- sponge brush or old paintbrush
- nitrile gloves
- lint-free cloth
Materials
- penetrating grout sealer
- paper towels
Steps
1. Check the Piece Is Ready to Seal
Three things have to be true before any sealer comes out. The grout must have fully cured for at least three days.
Tip: Three days is a minimum, not a target. Grout that still smells damp is not cured, whatever the calendar says.
2. Use a Penetrating Sealer
There are two kinds of grout sealer and the choice matters. A penetrating sealer soaks into the porous grout and stays inside it.
Tip: Read the bottle rather than the shelf label. Plenty of products described as grout sealer on the front are membrane formers on the back.
3. Method One - Paint the Grout Lines Only
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.
Tip: Load the brush lightly. A heavy brush floods the joint and runs straight out over the tile you were trying to avoid.
4. Method Two - Coat Everything, Then Wipe Back
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.
Tip: On a piece with hundreds of small pieces, method two is almost always quicker overall even counting the wiping.
5. Wipe the Sealer Off the Glass
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.
Tip: A dry cloth lifts wet sealer better than a damp one. Water just spreads it around.
6. Second Coat, Then Cure Indoors
Wait about 15 minutes and apply a second coat. Some brands want more than two, so check the label for the actual number.
Tip: This is the step people skip when they are already happy with how it looks. Sealing is what decides whether it still looks like that in three winters.
