Mosaic Q&A

answering questions about the art of making mosaics

Sealing wood and “dry” grouting — how to recuperate from improperly sealed bases

May 26

Posted by xinamarie in English, mosaic bases, mosaic techniques | No Comments

Question:

I was happy to find your blog on the web. For about 2.5 years I have been working on a table with two levels. I found the table on the street years ago and for a short period we put plants on it. It is made from fiber board. I started to work on the table during a class on mosaics. I have taught myself so much since the class. I apply plates, turquoise beads and some glass objects with AcrylPro. After working on the table for about a year I read about a woman who made a mosaic table but did not seal it first and the whole thing buckled when she applied grout. During the class our teacher had told us to sand our substrate but she never said anything about sealing. I once asked her what was her biggest mistake and she told a story about working on wood and not painting it first so it buckled. I have read many books since taking the class. I now know that one must sand and seal a wooden surface. I later looked at a sheet that the teacher gave us and read about sealing. Perhaps I thought I did not need to seal the table because it had this fake wood finish and some of the surface was painted. Since I discovered what I needed to do I have taken up sections and prepared the surface properly. My dilemma is this – there are some areas that are too intricate to take up. Also I am thinking that if I seal between the shards and even the sides of the shards then the grout will not permeate the wood. I have since sealed any areas that were not covered even the undersides. (I seal with WeldBond.) Do you think this will work? I would be happy to provide pictures if you need to see what I am talking about.

Answer:

What an interesting pickle.  On the places where you haven’t sealed, is the AcrylPro thick enough to cover the wood, or is there any wood showing raw?  The first problem is that fiber board with laminate covering is not the best base for mosaics in any case, because its not very long lasting or stable, but having that to work with, it really must be sealed.
The best way to seal is to use a product that will soak into the fibers of the wood, sealing these, rather than creating a skin on top of the surface.  If you think about it, the skin then becomes another layer of the mosaic, and your mosaic is now attached to the skin, not the wood.  To seal right to the fibers with weldbond, you should use a mix of 4:1 water to weldbond, so 20% weldbond to 80% water.   I too had an entire mosaic just slide off the top of an MDF base that i hadn’t sealed properly, and I had sealed the top, but not the bottom, so the wood itself wasn’t sealed, though there was a skin barrier between the mosaic and the wood — it got a few drops of rain when moving it to the car from under the roof where i was doing a market show, and that was it.  The wood swelled just a bit, and that was enough for the mosaic, still complete and sticking together for the strength of the grout, just slid right off, ‘skin’ barrier and all.
So, the dilemma is understood — question is what is the solution.  First, limit the areas that are unsealed.  That you have already done.  For the areas that are unsealed and there is nothing you can do about it, can you consider 1) simply not grouting?  if that is not an option, and will look really stupid, then I would try 2) injecting sealant into the joints, so that the spaces in between are covered.  Go with a weldbond/water solution and maybe a little syringe, and just squeeze it in the joints.  If it is runny enough, it should spread around to anywhere there are not tiles, and where there are tiles, the acrylic glue should provide a sufficient barrier.  I haven’t ever actually done this, but if I were in your situation, that is what I would try…
Then, when grouting, try and grout with a quite thick grout solution — different people grout in different ways, and the amount of water in the grout can vary quite a bit.  When i started out, I used quite a bit of water, and I used water or wet/damp rags to clean as well, but that was too messy and difficult, and i discovered that it is much easier and cleaner to grout with a thicker grout solution (mashed potatoes instead of sour cream…) and use dry paper towels to clean, rather than wet rags.  The trick here is timing — if you wait more than about 40 minutes to do the first cleanup, you have to use water, or it won’t clean. But if you wipe thoroughly with paper towels after about 20 minutes only, you don’t need to use water to clean at all.  Then the next, after the grout has cured (and therefore is covering and protecting the wood underneath) then you clean off the residue with windex or just soapy water.  But at this point treating with water should be relatively safe…
For my “dry” grouting method (its not dry, but it doesn’t use much water, so not much will come into contact…) see the tip sheet basic grouting instructions on this page on my site: http://www.xinamarie.com/mosaic/tips.php?osCsid=b179d3831c95769e551a0b96a0a903c3
I hope this helps!  And good luck!


Mosaic Tiling inside a bathroom sink or tub

May 16

Posted by xinamarie in English, mosaic bases, mosaic glues, mosaic techniques, mosaic tiles | No Comments

Question: Can I mosaic inside a bathroom sink or bathtub?  If so, what do i need to consider?

Answer:

It is possible, but very unusual, to put mosaic inside a sink or bathtub.  If you think of it as a very very small version of a swimming pool, you can see that there is no technical reason why you shouldn’t mosaic inside the sink or bath.  However there are a couple of practical issues.
First, you must glue and grout with a bicomponent expoxy product like Mapei’s Kerapoxy (we have this in stock in the common colours, and can order specific colours on request).  The epoxy grout will resist staining and will be much much easier to clean regularly than a cement based grout — daily toothpaste mess on cement grout will eat it up and muck it up in no time, but epoxy grout will be immune through time as well as daily cleaning!
Second, you must use a completely non porous tile.  Glass mosaic tile is the best for this — I would suggest Trend Lux — rich homogenous colour in a mosaic tile small enough (15x15mm) to get around soft curves (but not deep ones, be sure to choose shapes without tight curves), which you may well have in a sink or bath.  You should NOT choose a design or complicated mosaic that will require the tiles to be cut — their machine moulded smooth edges will be fine to touch, and smooth to sit on — but if you start cutting the tiles to make more complex artistic designs, you risk having sharp corners and edges that stick out.  Apart from making it more difficult to clean, these sharp edges could also make it uncomfortable to use or to sit in.
And finally, and perhaps the most difficult, the mosaic tiles will have to be installed onto a surface rough enough to grip the glue and the mosaic.  Standard bathroom porcelain is very smooth and shiny and slippery — epoxy glue is very very strong, but I would hesitate to use even it on such a smooth slippery surface.  If you can have the sink and tub purpose built out of cement, that would be perfect.  But if you need to use already existing porcelains, then I would suggest researching well to be sure how the porcelain should be treated so that the glues will work in the long term.  Perhaps just scratching up the surface with a sander or drill would work, but I have never tried so i don’t know for sure.

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How to hang wedi panels?

Apr 1

Posted by xinamarie in English, mosaic bases | 2 Comments

Question: How can i hang a mosaic made on wedi panel, particularly if cut in an irregular shape?

Answer: To prepare a wedi panel with a hanging mechanism, you need to

1) poke 4 holes in through the panel — two one on top of the other about 5-8cm apart on one side, and two one on top of the other same distance apart on the other side.  The larger the piece, the farther apart the holes should be.
2) Thread a long piece of strong hanging wire from the back through the top hole on the left, pull it down and thread it down the front and back out again to the back through the bottom hole.  Twist the pieces together leaving a single long piece to pull over to the other side.
3) Pull the wire across the back, then thread through the right side holes in the same way.  Twist together the pieces.
4) Press flat the small length of wire that comes on the front of the panel, use hot glue if necessary, to keep it as flat as possible.  You will simply mosaic right over this piece.
5) fill the holes with hot glue so the wire will not move in the hole, pulling and cutting through the panel with time.
And that’s it!  It leaves you with a wire strung across the back which you can use to hang the end mosaic.
This system is only valid for smaller pieces, up to about 80x60cm I would say.  I haven’t experimented with larger than that, but I fear the weight of the piece would be too much for the wire.  Bigger pieces can be framed, and hung by the frame (but that’s no good if its got an irregular shape! ) or they can be rested on a shelf — a thin but long “L” plate screwed into the wall, then rest the mosaic on the plate, and an “L” hook screwed into the wall at the top of the piece keeps it from falling forward off the “shelf”.


Steel or Carbide?

Mar 17

Posted by xinamarie in English, mosaic tools | No Comments

Question: Do I need a steel hammer or a carbide hammer for marble?

Answer: Steel for marble, carbide for glass!  A steel hammer will get dull, and a dull hammer sucks rocks (and not in a good way!), so do sharpen regularly.  In theory, and according to the instructions of the manufacturer, carbide shouldn’t need to be sharpened and can even be damaged by sharpening, but I’ve seen the guys at Orsoni sharpening them all the time, so the reality doesn’t bear out the theory.  But I will say, if you are going to sharpen a carbide hammer, make sure its an expert sharpener doing the work.  Carbide is very expensive and quite fragile!

Cosa uso per fare ciondoli a mosaico?

Mar 16

Posted by xinamarie in Italiano, mosaic glues, mosaic techniques | No Comments

domanda: vorrei provare a realizzare un pendente con un supporto che voi fornite, ma non so che tipo di colla si usa e che tipo di tessera, vedo che alcuni usano le tessere con l’oro.

risposta: Per i ciondoli, non ci sono grande restrizioni — io uso tessere di specchio, oro, vetro, millefiori, un po di tutto. Come colla, uso ultramastic III colorato, così cè anche un effetto stuccato senza dover stuccare.  Può usare anche vinavil, ma deve dopo stuccare perche vinavil può macchiare la copertura di argento, e lo stucco copre dalla vista tutti bucchi dove se vede lo fondo dove la colla ha toccato.

Cutting marble with wheeled nippers

Mar 16

Posted by xinamarie in English, mosaic techniques | No Comments

Question: Can I cut marble with wheeled nippers

Answer: Yes…IF it is already in smaller tessere format.  Marble is not as brittle as glass, and does not cut as easily with the wheel against wheel action of wheeled nippers, but if the pieces are already in tile format, then you can shape them without too much difficulty.  Leponitts will open wide enough for thicker material if you remove the tiny pin under the right side wheel (right side when you hold it facing you), but not all wheeled nippers will open wide enough for thick marble tiles.

Marble will also wear down the wheels very quickly, so its fine if you only need to do a few shaping cuts here and there, but not the best choice for regular repeated marble work.  Traditional sidebiters are a better choice for lots of marble work, and better still is hammer and hardie.

Encoller tesselles de verre su polystyrène, degradation de miroir

Mar 16

Posted by xinamarie in Francais, mosaic glues, mosaic tiles | No Comments

demande: Je souhaiterais savoir quelle colle je dois utiliser pour coller des tesselles de verre sur du polystyrène. J’ai entendu dire que l’argentil déposé sur le miroir pouvait s’oxyder. Merci d’avance pour votre réponse
reponse:
Les tesselles de verre peuvent etre encoller sur polystyrène avec colle PVA comme vinavil, ou avec ultramastic ou colle ciment (thinset).
Oui, les miroirs peuvent dégrader avec temps, mais les miroirs modernes sont beaucoup beaucoup plus durables que celles antiques — les technologies pour faire la miroir ont développer beaucoup dans les derniers 20 ans.  En general, c’est une bon idée d’eviter le silicone normale avec les miroirs, utiliser le silicone specifique pour miroir.
Aussi, attention avec la polystyrène parce-que il y en a des types qui peuvent creer les vapeurs veleneux si vous utiliser une colle chimique comme l’epoxy bicomponent.  Cela et une discours que je ne connais pas bien, je sais que le danger existe, mais je ne sais pas exactement les conditions pour le danger…alors rester avec les colles inertes comme PVA et vous etes au sécure!

Mosaic Q&A blog begins!

Mar 16

Posted by xinamarie in English | No Comments

I am a mosaic artist, and i run a webshop selling mosaic supplies and materials (see links).  Almost everyday, at least a few times a week, clients and mosaic curious folk ask me questions about mosaic techniques, materials, options on opinions.  For years, I have just answered the questions directly, and that was that (sometimes the same question a million times!)– what a waste!  Its only just now occured to me that these answers could be useful to lots of folks out there — usually if one person wants to know, there are lots of other people out there interested too!

So from today, I am going to post questions and answers that are asked me onto this blog — I will always keep the asker anonymous (unless the asker asks specifically to be identified!), and just post the actual question and the answer.

I have also answered sooooo many questions over the years, that I hope to go through some of the more common historical questions and put them here as well.  I will try to build categories as i go, so eventually we should have a nice little repository of mosaic FAQs all organised by technique type and subject.

I hope this becomes useful, and please feel free to sign up and follow all the time.

And feel free to ask questions!  I won’t always have the answer, but I will always try my best.  And other expert mosaicists out there, if you have alternative techniques, or other better answers, do post them!  The objective here is to get the best information circulating, and I’m not precious!  Won’t be offended to have alternative suggestions made!!

Ok, great…lets go!!

Cheers!
Christina