Making a mosaic trivet, Part IV: Grouting and finishing.
- Part I of this four-part series was about preparing the board: http://helenmilesmosaics.org/making-mosaics-2/how-to-make-mosaics/preparing-the-board.
- Part II covered choosing materials and a design: http://helenmilesmosaics.org/making-mosaics-2/how-to-make-mosaics/mosaic-designs-and-materials/.
- Part III dealt with cutting, laying and fixing the mosaic: http://helenmilesmosaics.org/making-mosaics-2/how-to-make-mosaics/making-a-mosaic-trivet/
Now it’s time to get down and get dirty. Roll those sleeves up, tie on your pinny and get out the rubber gloves – the moment has come to grout your mosaic.
NB: If you use porous stone as your mosaic material, then you need to apply a layer of varnish on the finished work BEFORE grouting to protect the stone and stop it ending up with a horrid grey film.
You’d be surprised how many people are not sure what grouting mosaics means, so just in case one of those people is you: grouting is when you fill in the gaps between the mosaic tiles to strengthen and protect the work. It also has the effect of bringing the piece together as a co-ordinated whole. It’s the most common method of finishing off a mosaic – but not the only one.
There are three ways of finishing mosaics:
1. Grouting the mosaic using tile grout – the same sort of grout as you’d buy to grout your bathroom or kitchen tiles. This lovely little thing from Scarab Glass Works shows very clearly what I mean – the grout is the grey bits. 
2. ‘Self -grouting’ : many mosaics are made by pressing the tesserae down into a soft adhesive which squishes up around the sides of the pieces and holds them down. The famous Byzantine mosaics are made in this way: 
3. Not grouting at all. The mosaic pieces will be firmly bonded to their substrate and if they are also placed close together, grouting is superfluous. This piece from Jacqueline Iskander is non-grouted: 
Before you start, you will need to make sure you have a way of getting rid of your excess grout – its nasty stuff, blocks drains and is generally yucky so you can either:
- Find a corner at the back of the garden (in the long grass, behind a tree) to swill out the used containers and rinse off your tools or
- Be ready to use lots of scrunched up newspaper and paper towels to give your tools and containers a thoroughly good clean after use.
I have a friend who once proudly told me she dealt with the problem by taking her grouting bowls out into the street and sluicing them off into the public drains…..Errr, no, that doesn’t work either. Any drain is a drain and the whole thing about grout – even watered down grout – is that it hardens and becomes as solid as concrete.
Right, we’ve got that clear, so the next thing you will need to do is to:
Prepare your tools and supplies
For this you will need:
1. Rubber gloves.
2. Plastic sheets to protect your surfaces/the floor under where you are working.
3. Two deep plastic bowls or buckets. Old ice cream containers will work just fine.
4. A spreading tool. An old plastic loyalty card is ideal for a mosaic this size or you can buy spreading tools at any hardware shop.
5. Two good, thick sponges.
6. Grout. I use Isomat Multifill Smalto 1-8mm, which means that it will fill joints up to 8mm wide. I also tend to use grey – not light grey, or cement grey or any other kind of grey. But just grey. I could write a whole separate post about grout colours but, for now, let’s keep it simple.
7. A spoon or implement of some sort to mix the grout.
8. A bottle/jug of water. I also find it handy to have one of those water spritz things which are used for spraying plants so that you can fine tune the amount of water you add.
9. Stiff plastic, scrubbing brush for cleaning.
Method:
1. Put your gloves on and make the grout according to the packet instructions in one of your plastic tubs. For a project of this size, you will need roughly two yoghurt pots of grout powder as I tend to ere on the generous side. Add the water in dips and daps and keep mixing until you get the right consistency – you are aiming for a paste: not runny, not with water sitting on the top, and not too firm. I read once that the best consistency is that of a cow pat and I regret to say that that is the analogy I always use.
2. With a sinking heart (it’s never easy), put a big dollop of this horrid, dark, goopy stuff on the front of your beautiful mosaic and use the spreading tool to push the grout into the gaps.
3. Cover the whole mosaic with the grout and don’t forget the edges:
4. Use your fingers to push the grout into all the gaps. You will find little air bubbles appearing as you apply the grout, so keep going until all the holes are filled.
5. Now use the spreader to remove the excess grout.
6. Fill your second plastic tub with clean water. Soak both of the sponges and squeeze out every last drop so the sponge is damp but not wet.
7. Wipe the front of the mosaic with the sponge – once – and then turn the sponge and using a clean side, wipe the mosaic again. It’s vital to always use a clean side of the sponge as otherwise you are just smearing grout residue over the cleaned parts of your work.
8. Keep going with both sponges, frequently rinsing them out and using fresh water until the front of the mosaic is clean. It will still look slightly on the grungy side, but don’t worry, that will come off in the final clean.
9. Leave to dry for a good, long while. There is no rush so better to leave it for more time rather than less. Once it’s thoroughly dry, get a stiff plastic brush, clean water, and give it a good, energetic wash.
10. Put four, little, felt self-adhesive patches (the ones hardware shops sell to put on chair legs) on the back of the mosaic so it can be put on a polished wood surface without scratching it.
Drum roll….Der, der! You’re done. Congratulations.
Keep tuned for the next mosaic project: making a mosaic on mesh.
Wow, Helen!!! This is a really superlative tutorial, so clear, so articulate, so confidence-inspiring, and, of course, the final result is absolutely beautiful!!!!!
Love the new website, too. You’ve been busy as a bee.
Fantastic!
Thank you so much, m’dear! Me, busy? Why it’s you that’s leading the way on all things bloggy and beautiful.
Hi,
I am from Bangalore, India. I dont find any classes where I stay for mosaics. its very people do it here. atleast i dont find anyone teaching when i looked up on internet.
i have collected scrap glasses, vitrified left over tiles, and terracotta tile in an attempt to make mosaic art.
glass failed as i have hard time figuring out using a diamond tip cutter and making precise cuts. breaking randomly is an option but however i would have been happy if i could have done how i wanted to.
i had a bit of issue to cut vitrified tile but soaking in water and then making a score line to cut did help in some way.
your site has helped me to learn given than i dont have classes.
my question.. you have mentioned to apply varnish on porous/unglazed kind of tesserae. since varnish would be runny and may settle in between the tesserae wouldnt it prevent grout applied later to adhere and not bond?
What are some materials that can be used if grout not used. would using silicone sealant/caulk be sufficient?
Nagashree
Hi Ngaashree, Good to hear from you! The varnish I use is thick (ish) and not all runny so I don’t have the problem of it settling in between the tesserae. It’s a special varnish for stone – do you have anything like that over there in India.
A lot of mosaic artists don’t grout their work so you don’t have to if you don’t want to. They press the tesserae directly into a concrete based mixture (like tile adhesive) so that the mixture comes up between the tesserae and self grouts.
If you haven’t already, then I’d really recommend that you join the Contemporary Mosaic Artists website http://mosaicsandceramics.ning.com/ as they have lots of practical information and forums and groups that you can join and share information and get advice. It’s really, really useful.
All the best, Helen.
Fantastic information. An alternative to applying to mesh first. Thank you,
Thank you so much for this fabulous tutorial. Since I am nowhere near Edinburgh or Greece (so unfortunately cannot attend your classes) and discover a dearth of mosaic artists in Pittsburgh, PA, USA … these beautifully done blog posts are invaluable and much appreciated.
Thank you Rebecca. That is so nice to hear. Don’t forget that you are extremely lucky to be living near Rachel Sager of the Ruins Project https://sagermosaics.com/ who runs classes as well as Anabella Wewer https://www.cositasbyanabella.com/work/ both of whom are extraordinary mosaic artists. I don’t know about the geography of PA but being in the same state is surely a good first step!
I need some ideas on the best way to grout a rectangular wood flower planter made with broken china. The only things I’m seeing are for round ceramic pots even after I specify
I would grout it the same way as a round ceramic pot, using the same materials. It is unusual to use a rectangular wood planter which is why you have not finding information about it online. Wood is not recommended for outdoors although marine ply will be fine if you seal it before use.
That mosaic by Jacqueline is not grouted because you don’t grout Classical mosaics made with marble and smalti, nor is it a trivet. It’s in a floater frame, on a wall.
Very true, Tracy! I didn’t say it was a trivet but that it was an example of a mosaic which isn’t grouted.
Hello
I am having problems with tiles (especially edge tiles) coming off during grouting – do you know what might be causing this? The tiles feel solidly stuck down but then once the grout goes on some of them start to come loose. I’m not sure what I am doing wrong. I would be grateful for any suggestions!
Thank you.
Hello Abigail. Don’t worry, it is a common problem and I find that the key to avoiding it is to give the mosaic a REALLY good brush with an ordinary largish (3″ +) paint brush before grouting, being rigorous in the process so that any pieces that might be stuck but not stuck enough will reveal themselves. The other issue it could be is the glue you are using. I have started to use a glue called Titebond II which is officially a wood glue but is 100 per cent waterproof and outdoor weather proof and dries rock hard. I find that PVA can be patchy sometimes and not always reliable. I hope that helps.
Hello, I am new to this website but looking for some advice regarding how to seal trivets so they don’t get stained & can be wiped easily? I have used glass tiles mostly but it’s more the grout I’m worried about. Should I used varnish? Or use same sealant for grout that I would use outside?
Interesting that you should ask, Anne, as I was having a conversation about this very topic earlier in the week. Yes, you should use a grout sealant which is suitable for outdoors rather than a varnish as the varnish would quickly deteriorate if hot things were put on it.
Many thanks Helen!
I am trying to order Multifill Smalto grout but it seems that it is only available in Greece. are there other grout brands you recommend that I might be able to get in the States? I am looking at Polyblend Plus Non-Sanded Grout, but it says 3mm, which I think is probably too large for a marble mosaic. I don’t know how to proceed!
Sorry for the late reply – yes, I use BAL Grout Flex in the UK. As long as you choose a grout which is suitable for outdoor conditions and for the width of your interstices then you should be fine. https://www.toppstiles.co.uk/fixing-finishing/grout/bal-grout-flex-mid-grey-5kg?gclid=CjwKCAjwitShBhA6EiwAq3RqA8OKV_-2b1wHhswMRG2QDE3E39M4CfUjwvR9O3G_LlGbJhWlqfQ7-hoCvhIQAvD_BwE&gclsrc=aw.ds