Question from Carolyn

Hi Brett,

I have just joined your site and have been studying the tutorials and the articles. It’s all been very interesting and very motivating. However I am having trouble with the glue at the moment. In the past I have just had small projects and just bought a tub of prepared tile glue and all was well. Recently I bought some cement based powdered glue which I have been having trouble with as pieces seem to fall off quite easily and it is hard to know the right consistency – in fact it’s been a real mess quite frankly. So I’m not sure where to go from here. I think I prefer using the prepared glue in a tub. Is this OK long term in your opinion?

Next question. Can you advise me on ways of using epoxy resin and mosaics. I’ve seen a bit of this around with people making rubber door mats with pebbles on top and was wondering how it was done. Any suggestions?

Thanks very much for the site.

Reply from Brett

Hi Carolyn

Thanks for your post (and good questions too!)

OK cement based glue.

When I refer to cement based glue, I’m always referring to polymer enhanced glues – that is, they add plastic or rubber products to the glue to aid flexibility , bonding and a range of other benefits like increased “”pot life””.

If you’re using a straight out cement product, it’s going to be pretty vulnerable unless the substrate is completely rigid porous. For example, I wouldn’t hesitate to use plain cement glues on terracotta concrete pots (I would prime surfaces first though)

If you’re going to use cement boards, plywood (completely sealed) or similar surfaces, then a polymer added glue is essential. I’d also rather this type of glue for underwater installations.

For larger projects. fixing to non-porous surfaces or situations where there is any doubt at all, I use a further additive to add more polymers for even better performance. This is the system you’d use for non-porous tesserae too.

You can even buy cement glue additives that will literally flex like silicone and therefore stick to basically anything – not that you’d need them often, but they are actually available!

So whilst I understand that you can use many different glues for mosaic work (particularly for indoors), I recommend cement glues with varying degrees of additive for the job at hand.

I think (but can’t be sure) that most tile glue manufacturers offer something similar – I use RLA polymer products.

The cost is pretty much irrelevant in my view – it probably costs $20 per square meter for a very high quality glue system – nothing compared to the final value of your artwork.

Now it does take a bit of practice to use these types of glue inevitably there is more mess, but by using plastic bags as I suggest in my tutorials, you’ll quickly get used to it, and will eventually work with less mess.

Glue consistency should be similar to toothpaste, but it has to be sticky – if the tiles don’t stick well while you’re laying them, they won’t stick well when dried either. Throw out prepared glue that isn’t sticky, and remove glue on your project that has “”skinned”” – it just won’t work.

To answer your question about using prepared glue – it’s fine for indoor small projects, but it gets riskier as your projects get bigger more diverse. I’d really rather use what I’m suggesting, and concentrate more on the artwork than worry about whether the glue will hold.

I’m not really too sure about your question about epoxy – are you referring to using epoxy resin to cover the entire project, or using it as a glue? If you could let me have a bit more detail, I’m happy to talk about this one as well.

Cheers – I hope that helps.

Brett

Reply from Carolyn

Thanks for that answer Brett, I’ll take that on board and have a good talk to the man in the tile shop, and I agree, you definitely don’t want to be worried if the glue is going to work or not, you want to be more concerned about the artwork.

As to Epoxy resin, the door mats I saw looked like they were stones stuck onto the rubber mat and then completely covered with a clear resin. Perhaps the resin had been poured over and into a mold. I’m not sure. Any ideas?

Reply from Brett

Hi Carolyn

Yep, it sounds like it would be epoxy resin poured into a mold. The only thing that confuses me about this, is that epoxy wouldn’t be a great choice as a doormat as it would scratch badly from foot traffic.

I’ve looked into using using an epoxy coating on mosaics a couple of times before as I know others have used it and it sounds like an appealing finish.

I’ve been put off for a few reasons:-

1. there’s no guarantee it will bond well with glossy tiles and would cause nightmares if it did start to come away as you’d never remove it all – especially from the grouted parts.

2. According to the owner of the fibreglass shop – there are no epoxys or acrylics that won’t yellow in the sun

3. any coating like that would scratch far more easily than ceramics. You could get around that my sanding the work back recoating, but that’s not really an attractive proposition (particularly for clients).

So if I were to use it, I’d stick to indoor decorative pieces rather than functional pieces or trafficable pieces.

That’s about all I know about the subject. I’ve used the resins to make fibreglass (an excellent substrate for murals), but it’s pretty labour intensive and messy (not to mention very expensive).

Hope that helps.

Cheers