I tried weathering some boxcars with chalk for the first time today and thought I was doing OK. That is, until I sprayed on some Testor's Dullcote and blew the chalk away. The Dullcote when dry also seemed to obscure the details.
Do you guys "overdo" the chalk weathering so that you'll leave the right amount behind afterwards? I've also thought about holding the spray can a couple feet away to reduce the blast.
You need to 'grind' the chalk into the surface with a stiff brush. Enough will adhere, or penetrate, to stay in place when it's dullcoated. But, as you've discovered, some will usually blow away.
Also, the dullcoat tends to lessen the effects of the chalk that remains. It tones it down. This is especially true of light chalk colors. This 'lessening' is often desirable, as it makes over doing the weathering difficult (a common problem). You can always add more if needed. With experience, you can gauge this, and apply just as much as needed to get the final effect you want. And, with the chalks, if you louse it up, you can usually remove most of it BEFORE you dullcoat it. It's the most 'forgiving' weathering technique in this regard.
Chalks are great for many effects, but do not replace washes, mists, splatters, and especially dry-brushing. ALL are useful weathering techniques, and each produces different results. The best weathering jobs usually use several of these techniques.
This is a known problem. Something about Dullcote makes it marry into the chalk dust and turn it invisible. On structures, which don't get handled as much as rolling stock, I just omit the Dullcote. For rolling stock, I don't have a good answer yet. So far I just don't weather rolling stock with chalk.
In case you didn't do it, a coat of Dullcote should be applied before you use the chalks. In addition to a firm bristle brush, I use a Q-tip. I find the Q-tip will force the chalk into the base layer of Dullcote better than a brush.
1st of all, stop using Dullcoat. Its the worst thing you can put on a model. It's just talc and laquer. It absorbs, hides, marries into, whatever and makes chalk vanish. I prefer Krylon Workable Fixatif #1306 (thier spelling, not mine). It was originally formulated to seal pencil, pastel and chalk drawings, and when properly applied, hardly diminishes the chalk at all. I get it at my local Jo-Ann fabrics, its right next to the chalk! Only 1 drawback, it leaves a slightly satin finish. I usually hit this with a light dusting of Floquil flat finish to kill the sheen. But if you must, go ahead and empty out that can of Dullcoat. Once its "fixed" I doubt even that could hurt it.
This is exactly true. The 'raw' chalk dust just lays on the surface as minute granules. These reflect and scatter light, and make the chalk seem prominent. This is especially true of white or other light colored chalks. They look 'light' almost entirely because of the light they scatter. White chalk isn't really 'white' at all, but a matrix of tiny clear granules (crystals). Each chalk grain is like a tiny diamond, reflecting light. Add thousands, or millions, such tiny points, and the result LOOKS 'white'. It's NOT. Dullcoat it and reduce the surface scatter, and the effect largely 'disappears'. When you dullcoat the chalk, the granules bond to the surface, and the lacquer fillets around it, so the grains are no longer separate entities lying on the surface. This greatly reduces the chalks ability to scatter light, it appears to 'darken' considerably, and loses SOME of it's color intensity.
An excellent 'dusty' effect can be achieved with just the 'raw' chalk, but even the slightest contact with your hand will leave prominent fingerprints, where the chalk adheres to your (always moist and oily) skin. Similar handling problems occur with the 'metalizer' finishes.
The chalk can be left 'raw' as long as you DON'T handle the item. As you say, this may work fine for structures. For rolling stock, and other things that usually must be handled, it's far better to seal the chalk down with 'dullcoat' of some type. Most of the 'dusty' effect can still be achieved, but with the overcoat more, and thicker, applications of the chalk are needed.
I like Testor's Dullcoat, with reservations. I've NEVER had it 'yellow', 'alligator', or flake off like several other coatings I've tried. It's durable, and rarely wears off or 'glosses' from handling. Put on properly, the coating is thin and does NOT hide detail. ALL flat finishes have talc or some similar material in them. They produce a 'flat' finish by making the surface rough at a microscopic scale.
The biggest problem with Testor's Dullcoat in spray cans is inconsistency. One can will work great, the next won't 'flat' as well it at all, and occasionally you get a 'disaster'. Usually the problem is not the Dullcoat, but the spray can. Some spray a fine mist, others shoot a near stream that's uncontrollable. Still, the cans are handy, and often work quite well (just don't TRUST an 'unknown' can).
Some tips on using the spray cans (Dullcoat, and many others) ...
SHAKE the can VERY well.
WARM it up in a pan of warm water before spraying. Cold dullcoat will 'blush' and turn white when it dries. Cold cans also have insufficient pressure to atomize the spray properly, and will spatter the liquid in big drops instead.
*CLEAN the nozzle with solvent if there's any lacquer build up on the tip, or an odd spray pattern.
*Don't trust OLD cans ... if it's more than a year old use it up on scenery or other non-critical projects.
*Don't use that last little bit in the bottom of the can ... it may have WAY too much talc in it.
*TRY the can FIRST on some non important item or surface.
*When finished spraying, INVERT the can and spray until just gas comes out. This will clear the paint passages so they don't clog between uses.
Better yet, avoid the spray cans altogether for your better work. Get the bulk bottle of Dullcoat and use it with an airbrush. THAT works MUCH better! MUCH better!
"George" use the chalks. In addition to a firm bristle brush, I use a Q-tip. I find
Yes, this is another option that has been mentioned in the model RR press from time-to-time(Lionel Strang?). Applying the Dullcote first provides "tooth" which results in better adherence of the chalks. i.e., the chalks won't rub off easily, even if frequently handled. If you feel you have overdone the weathering using this method, then a light coat of dullcote is in order. Still dissatisfied? Try again.
I've actually had descent results, reversing the steps.. Spray the car with a very light layer of Dullcote, then sprinkle/sift the chalks on. Drag a dry brush, roof to bottom sill untill you get the desired effect. This represents, of course, natures rain path is it drips off the roof and down the side of the car. Repeat as nesecary. I find the chalk will 'stick' to the wet surface of the Dullcote, whereas the Dullcote will obscure any 'dry' weathering by absorbing the chalk..
Just my 2 cents $CDN. 1.35 of a cent $USD _______________________________________________________ Drew Bunn Ainsley Specialized Transport Toronto, Ontario Canada bunn email@example.com