Using DAS on plasticard structures

[Captain Kernow]

I am planning on building a 4mm brick and stone structure, using plasticard as the basis but with DAS cement on top, scribed to represent an individualistic pattern of brick and stone.

I'm sure I've read of DAS being used on plasticard buildings before, but does anyone have any tips to help the DAS adhere properly to the plasticard, please?

I am assuming that the surface of the plasticard will as a minimum have to be roughened.

Thanks.

 

[76043]

I've applied PVA to bluefoam and found it mostly has stuck, but don't think it's ideal. I can't recall what Gordon Gravett does, is that DAS on card?
Tony

 

[GWRfan]

Hi @Captain Kernow The problem is that DAS, like a lot of air drying clays, shrinks as it dries, pulling away from whatever it's based on, and warping stuff it can't pull away from. Even if you use pva glue some parts will still pull away.
I have seen on some YouTube videos that when working with das clay dampen the surface of the plasticard as the clay adheres better but try and let it dry in a cooler place so it drys out at the same time and it's more controlled.

 

[George M]

https://flic.kr/p/rR1yzh

I frequently use Das or equivalent over plywood. Yes, it does shrink, about 10%. But, if you lay it into a bed of glue that dries faster than the clay, virtually all the shrinkage will be confined to thinning of the clay. You can further control the shrinkage by carving joints into the clay while wet.

Alternatively you can make the clay plates on a flat surface off the model and glue them in place after they have dried, blending in the joints with fresh clay. I found this out the first time I tried clay and did not use glue. The clay shrank and fell off the model in plates so I had to glue it back on!

 

[76043]

I've used the DAS with glass fibres and it's pretty good at not shrinking.
Tony

 

[Bulldog3444]

Hi Tim,

If I recall correctly Geoff Taylor did a video on this at one of the Missenden Modellers virtual events during lockdown. I think that he put a layer of thin PVA on the plasticard base structure before laying the DAS on top of it - working on sections of the wall about an inch square at a time.

Worth having a go as a trial and seeing if it works for you.

Ian

 

[Pencarrow]

Got the t-shirt on this one CK...

Super glue is the answer on roughed up plasticard.

I put a few spots of glue on and then cover with blobs of DAS. Once the glue has set you can place the rest of the DAS in between the previously applied blobs. Didn't have any issues with shrinkage.

Used this method on the Polsarrett clay dries.

I found that PVA doesn't always bond that well to plasticard unless it's very rough.

 

[Captain Kernow]

Thanks everyone for the comments and suggestions so far.

I was thinking of scribing the stonework on the dried-out DAS (once sanded to an acceptable finish), but I'm getting the impression that this may not be recommended, as compared to scribing wet DAS? What are people's experiences of scribing dried-off DAS?

I do know that tile grout is fairly easy to scribe when dry, also Polyfilla type fillers and based on my positive experience of scribing the cobbles on Callow Lane, I was thinking of using tile grout on top of the plasticard, so presumably either flooding the dried tile grout with MEK or applying it just before the tile grout would still work? (or applying some blogs of tile grout with super glue, as per Pencarrow's suggestion and then applying more when dried?).

The structure this is meant for is a road-over-rail stone bridge.

Thanks.

 

[76043]

I'd still be tempted to follow Gordon Gravett's scalpel on this, he uses card for his shells doesn't he?

Behold, it's a sign, follow the scalpel!!

Tony

 

[Pencarrow]

Thanks everyone for the comments and suggestions so far.

I was thinking of scribing the stonework on the dried-out DAS (once sanded to an acceptable finish), but I'm getting the impression that this may not be recommended, as compared to scribing wet DAS? What are people's experiences of scribing dried-off DAS?

I do know that tile grout is fairly easy to scribe when dry, also Polyfilla type fillers and based on my positive experience of scribing the cobbles on Callow Lane, I was thinking of using tile grout on top of the plasticard, so presumably either flooding the dried tile grout with MEK or applying it just before the tile grout would still work? (or applying some blogs of tile grout with super glue, as per Pencarrow's suggestion and then applying more when dried?).

The structure this is meant for is a road-over-rail stone bridge.

Thanks.

CK, I used a particular sort of DAS as below which is grey and has a stone finish.


I tried both scribing whilst wet and dry. In the end I went for both. A rough outline when wet and finishing off when dry. Once I was happy with the finish I brushed over it with watered down PVA (ballast mix) to toughen it up. Then I sprayed on grey Halfords primer before painting.



There's a mixture of DAS stone blended in to the original resin building in this building above.



The wall in the left foreground is DAS on a plasticard former.

 

[Pencarrow]

Found a few more progress and finished photos here @Captain Kernow

 

[Pencarrow]

PS, I'm wondering if the lack of shrinkage issues is down to the use of the stone DAS product rather than the normal clay stuff? It definitely feels and looks different in use.

I also just remembered that I used it for the roads and goods yard surfaces on Polsarrett. Again no shrinkage cracking issues noted.

 

[76043]

I've used the stuff with fibres in and have found very little shrinkage.
Tony

 

[DavidB]

I would be inclined to roll out the DAS, create the finish then let it dry before attaching it (if you feel the need) to a building framework. Rolling between two 'sticks' of suitable depth will give you a uniform thickness.

 

[Pencarrow]

I would be inclined to roll out the DAS, create the finish then let it dry before attaching it (if you feel the need) to a building framework. Rolling between two 'sticks' of suitable depth will give you a uniform thickness.

Unless you're breaking it into stone blocks and then fixing them individually to the carcass, I think you're going to have issues. I have a suspicion that it wouldn't dry flat as the rear of it will dry slower (being not open to the air) than the front.

Be interesting to see if it's been tried and at what thickness.

 

[DavidB]

I agree is the DAS is thick, but I would experiment. If it is thinner, it shouldn't be a problem.

 

[Giles]

I also use Das Stone, and it does shrink less than the original stuff - it's much better!

 

[SimonT]

Another vote for Das Stone (" One ping Vasily, just one ping" ). Keep it in a sealable bag in the fridge.

 

[Captain Kernow]

Thanks for the tips re DAS Stone, I shall certainly get some and experiment.

 

[David Waite]

May I ask what is the physical difference between the Das Stone and the standard Das modelling clay?
David