Pointing turned white, but not efflorescence! - Pointing turned white, but not effloresc

[Brucieboy]

Hi fellas, just picked this thread up again. I think you're confusing dyes (used to colour clothing etc) with pigments. The UK mortar industry uses predominently synthetic iron oxide pigments conforming to BS EN 12878:2005 - Pigments for the colouring of building materials based on cement and/or lime - Specification and Test Methods. The reason they're called synthetic is because they are not naturally occurring. Most are made by dissolving metal swarf (a good proportion of which comes from the car manufacturing industry) in either sulphuric or hydrochloric acid. Global manufacturers include Bayer (Germany) and Cathay (China).

The UK mortar industry (dry silo, ready-to-use and lime:sand) usually uses four base colours - yellow, light-red, blue-red and black and blend as required to produce the various coloured mortars supplied every day. Some mortar producers use powders, some use granules (about 1mm diameter - the latter flow more easily than powder in the production plant). We used to use liquid pigments some years ago but these were prone to settlement of the solids (the powder) over time giving all sorts of handling and dosing problems. In the end we gave them the boot although to my knowledge they are still available. Pigments for special colours are white (titanium), green (chromium) and blue (cobalt) all of which are very expensive. There are also some naturally occurring iron oxides such as ochre which produces yellow through to reddish brown.

I'll be very surpised if Easipoint do not use pigments as described above (I'll check with them tomorrow to be certain and let you know either way). Cementone, as mentioned in my previous post, do.

The most likley reason hand batched coloured mortar fades more so than Easipoint is probably due to misuse. Parex no doubt weigh batch all materials so the proportions are consistent, use materials that are consistent in quality, e.g. clean, well graded silica sand and most likely include an admixture (probably powdered SBR) and one or two "secret" enhancers that they've found to improve the product over the years.

Given the choice without any budget restrictions, I would undoubtedly opt for Easipoint.

[lutonlagerlout]

i think the biggest problem with the powder dyes that you buy is that effectively you have to use nearly a KG of powder per mix
so the cost rockets
LLL

[Brucieboy]

I agree, pigments are relatively expensive. However, it's the same for Easipoint although they can no doubt buy their pigments at a better rate than joe public due to bulk purchase, as does the mortar industry.

[lutonlagerlout]

am i correct in thinking bruce that pigments are better than dyes?
i have a mate who has a phD in dyes and he has told me stuff but its a bit of a non starter in the pub talking about dyes in food production :;):
LLL

[Brucieboy]

LLL - dyes are generally used to colour textiles, food etc whereas pigments are used to colour concrete and mortar (hence the title of European standard I referred to above). One's not better than the other, just used for different purposes. Some dyes are organic (plants, wood, even fungi), some are synthteic (man-made). So when referring to coloured concrete and mortar - it's best to use the term "pigment" as described above, not "dye". I'm not a chemist, but I've been using pigments for donkey's years.

Up to about 10 or 15 years ago, some of the less informed mortar producers used to use "carbon" black as opposed to iron oxide black. Carbon black is a relatively cheap, extremely fine powder which gave a really rich black coloured mortar. The only problem was after about 18 months to 2 years, the carbon particles, being so fine, washed out from the surface of the mortar joint leaving the normal grey colour. Basically they weren't locked into the cement matrix and came adrift on weathering. If anybody made a fuss (normally the architect), the mortar joints had to be tinted by a construction cosmetics company at significant cost or the supplier risked a legal battle. It didn't take many of these to make the supplier change over to iron oxide. Hope this helps.

[ohcrumbs]

Sorry, another newbie problem!...

Do any mortars go darker when they're wet? A problem that we have with matching our granite & basalt stone is that the stone appears much darker after the rain...

Would a mortar we colour ourselves go darker after the rain? Or would easipoint?

Cheers!

[Brucieboy]

Most mortars, concretes and paving go darker when when wet. The darker the natural colour of the paving, e.g. basalt, the less noticeable the difference.

If you're colour matching, you have to let both mortar and paving dry to their natural state before establishing the match. This could take a quite a few days depending on weather conditions. Don't make a decison before. You could try force drying a piece of hardened mortar in a microwave (medium heat) and, when dry, break it in half to get an idea of the finshed colour but, bear in mind, tooling a joint at the time of pointing will have an effect.

Not so sure about Easipoint as I said before I've never used it but I'm reasonably certain the same principles will apply. You'll probably need to carry out a trial with a sample to find out if it suits you - have a word with them if you're still in doubt. I'm sure other guys on this site will also provide some additional advice.

[KAMIKAZEE DIY]

Has anyone ever sourced black sand to make a dark mortar?

From browsing forums it appears success with dyes can be short lived. I've seen black sand online, maybe a bit more expensive but I can't see why it shouldn't work and give a permanently dark mortar that main site recommends.

Did pointing before 3/1 sand cement but it was quite bright white. Hopefully with black sand you could still go 3/1 but get right colour.

Cheers

[Tony McC]

Using black sand seems like an obvious idea to achieve a darker mortar but it's actually the cement that forms the paste and thereby determines more of the mortar's colour. Mix a black foundry sand with OPC and you will still get a grey mortar with dark speckles.

What you need is a darker cement and that would suggest something other than OPC. PFA is dark and a bugger for going darker when exposed to the atmosphere, so would seem to be an obvious choice, but making mortars and concrete with PFA isn't really a DIY task.

If you really must have black or very dark mortar, then a resin mortar is the better choice. The resin tends to be colourless, or nearly so, and therefore the colour relies mostly on the fine aggregate, often a dark granitic or basaltic sand.

[dig dug dan]

Has anyone ever sourced black sand to make a dark mortar?

From browsing forums it appears success with dyes can be short lived. I've seen black sand online, maybe a bit more expensive but I can't see why it shouldn't work and give a permanently dark mortar that main site recommends.

Did pointing before 3/1 sand cement but it was quite bright white. Hopefully with black sand you could still go 3/1 but get right colour.

Cheers

Easijoint do blak pointing mix if thats any help?

[KAMIKAZEE DIY]

Tony, thanks for the informative reply, interesting.

Dan, thanks for product recommendation. Had a look at it, could be what I need. Can you polish joint to a nice smooth finish or does it have "polystyrene" look if you know what I mean?

Cheers

[Tony McC]

GftK 840+ is the 'blackest' resin-based jointing medium I've seen, but it's a polymeric (one-part) so nowhere near as good as the two-part products (800/850/Romex D1/etc.) which tend not to be quite as dark for reasons only the Germans can explain.

[dig dug dan]

Tony, thanks for the informative reply, interesting.

Dan, thanks for product recommendation. Had a look at it, could be what I need. Can you polish joint to a nice smooth finish or does it have "polystyrene" look if you know what I mean?

Cheers

You can smooth it off with a pointing iron once its in, but never have as it looks ok as is.