Why is alcohol better than water for filling in the mortar cracks?

[Anonymous]

Why is alcohol better to use than water when it comes to mixing with paint for filling in the mortar cracks on structures? I used water on two previous buildings mixed with gray Pollyscale paint, and the problem I'm having with it is that the cracks fill up and look good for about 20-30 seconds or so and then disappear, then the brick is left with some gray paint on it and very little if any in the mortar cracks. Some small spots look great, but most don't. I'm trying to get the right mixture of paint and water, thinning it down, etc., but as a newbie I guess I'm still not getting it correct, as I'm not happy with the results. I haven't used the alcohol so far because we only have the 70%, not the 91% or whatever.

But does the alcohol/detergent/paint mixture work the best (instead of the water/paint mixture) when it comes to filling in the mortar cracks? Will I see better results with the alcohol/paint mix? Will the alcohol/paint mixture cause the paint to stay in the mortar cracks better than the water/paint mixture does? And what does the detergent have to do with it? I'm currently working on the Bachmann 'Spectrum' Series 'Cityscenes' Department Store, with 2 large walls with lots of brick. The other 2 walls aren't too bad.

[Anonymous]

While I'm not sure about the answer to this question, I will give some information based on what I do know. The detergent helps to break the surface tension, from what I've been told. This means that it helps the paint to stick to whatever you're applying it to. As for the alcohol vs. water, the advantage that I can see is that alcohol dries much more quickly, causing the paint to stay put more easily. Even if you don't have the 91%, the 70% should work better than water for the reason stated above. I haven't tried this at this time, so I'm only passing on what I've heard and read about these things. Hopefully there will be others who can help you more than I can.
-Joe

[rrinker]

I haven't tried doing and mortar lines yet, but for a ballast test I tried 70% alcohol and glue instead of water/detergent/glue, and the 70% alcohol/glue did a MUCH better job that the water/glue.. I suspect you will be ok with the 70% alcohol.
Alcohol has a lower surface tension, and allows the paint (or in my case glue) to flow into the cracks and crevices better. To get wtarer with detergent to do the same, you'd need fairly soft water and the right amount of detergent. The harder the water, the more detergent. And the detergant must be eavenly distrubuted in the water for this to truly work - lots of stirring, because if you shake it - well, you can figure out what happens there.
I have a couple of Walthers building kits that need mortar lines, I'll have to give the alcohol a try there as well. I know I am definitely using alcohol to do my ballasting.

--Randy

[mcouvillion]

NS82,

The alcohol has a lower surface tension than the water, so it settles down into the small cracks and crevices a lot easier than water would. Detergent in water reduces the surface tension of the water.

You can visualize it yourself. Take a small mirror or other plate of glass. Place a drop of water on the surface. It should ball up a little. If you place the drop of water on a piece of waxed paper, it will really ball up. Now, place a drop of alcohol on the mirror or waxed paper. It will settle out and flow. Same thing on the model surface.

Mark C.

[davekelly]

I've used 70% alcohol when doing the mortar on my buildings (acyrilic paint). It works great. I would suggest, however, you practice on a smaller project before tackling that Bachmann department store, that way if it doesn't turn out the way you want it to, nothing is lost. Perhaps a couple sections of the DPM module system would work to practice various dilution amounts, color etc.

[Anonymous]

Slightly related question, as I'm about to do some mortar filling on a roundhouse I'm building -- what ratio of paint to alcohol do you use? I figure the wash has to be pretty thin, but not as thin as the grimy black wash I use for basic weathering (10:1 thinner to paint). What's good for mortar -- 7:1? 5:1? ???

[davekelly]

To be honest, I don't know the ratio as I just keep adding alcohol until it is "very thin" I'm guessing it's somewhere between 7:1 and 10:1. I think it is easier to make it a little on the thin side and then add paint to it.

[Anonymous]

Thanks! That's what I figured.

[Anonymous]

I have used Phot Flo solution and Poly scale paint for my mortar cracks and it seems to work very well. I will mix 18 parts solution plus 4 parts thinner to 2 parts paint. I find this works very well. Make sure you give it time to dry. Cover the entire surface with the mixture by dabbing it on insted of trying to brush it on. You can purchase this at a camera store.
Let me know if you try it and how it works for you.