I have only recently started building my first model railway and have a question about scatter and using PVA glue. I was told a mix of 30/70. Now I am assuming that means 30% water and 70% PVA and not the other way round.
Is that correct?

Quote from: geoffgil on April 03, 2019, 05:44:56 PM
I have only recently started building my first model railway and have a question about scatter and using PVA glue. I was told a mix of 30/70. Now I am assuming that means 30% water and 70% PVA and not the other way round.
Is that correct?

There is no single correct answer; it will depend on the native, undiluted strength and fluidity of the glue...
PVAs intended for outdoor use tend to be stronger and thicker so more water will be needed. If you buy it from the kids department of the local craft store it will likely be thinner and weaker so may not need much water if any at all...

For ground scatter I usually squirt a blob of neat PVA in the middle of the area then dip a reasonably large old paintbrush in water and use that to spread and thin the glue.  After applying the scatter I usually then soak it through with 50/50 PVA/water mix (same ratio as I use for track ballast) and then sprinkle a 2nd top layer of scatter (I use the foam granule types not the sawdust types).  This is because I like to make the base ground cover solid and "finger proof" as it's for an exhibition layout.

Ok thanks for all your help. I think I will do some experimenting, before I do the real things.

Yeah, experimenting is the name of the game. Different jobs require different techniques.

ntpntpntp's technique is a good one. For small fine detail areas I sometimes use a small pipette and apply glue as I would to ballast. Foliage clumps etc  are fixed using straight pva.

I usually prime the area with a 50/50 mix of PVA/water, apply the scatter with a cheap plastic sugar shaker and then, using a cheapo spray bottle, overspray with the same 50/50 mix but with a couple of drops of washing up liquid added.

Thanks for all your help. Its obvious that there a number of ways of tackling this. I will try all the ways suggested and decide what is best for me.

i'm a 50/50 guy just to throw my opinion into the mix.

I don't think there's a perfect ratio. It'll depend on how watery your PVA is, to start with. I always aim for a milky mixture that runs out of the pipette easily.

While I do add a drop of washing up liquid, I don't rely on it, and instead use a spray bottle with IPA (isopropyl alcohol, not the beer) to break surface tension. Pipette out the glue onto the ballast, spray with the IPA, and the whole thing runs and sets very nicely indeed.

IPA is incredibly useful, so well worth buying. It's good for cleaning electrical contacts on locos, cleaning dirty track, even removing some types of paints.

Cheers, NeMo