See if this helps.
How to Create a Tarmac
by Florian Kapsenberg
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This is a guide on how to create a realistic looking scale tarmac for your scale aircraft, in every step take into account the scale you are working in and reference pictures don’t hurt either. Using this method you can finish in less than a day.
I have found that using a piece of gray card board (the kind you will find on the back of a notebook) works out very well, but I am afraid it may discolor a bit after a few years, then again, that’s just me. Go ahead and glue it onto piece of plywood with wood glue on the entire surface and compress it for a few hours until the glue has hardened so it wont warp as time passes.
For this technique you will need to draw a grid on your piece of cardboard (NOT AT RIGHT ANGLES TO THE EDGES OF THE CARDBOARD!!! it looks extremely tacky) at about a 20-degree angle to the side of the cardboard. Once you have your grid drawn, get out an object with a blunt point (I used a knitting pin). This will create an actual groove that will stay, no etching involved! Once this has been done, you can retrace the lines with a slightly sharpened pencil to redo the lines that might have faded because of the groove making. Have you ever noticed that the grooves in a tarmac have some rubber in them (usually in the intersections, edges and along some of the heavily used areas)? This affect can easily be achieved using slightly thickened dark gray watercolors. Be careful not to put too much on the grooves or the scale won’t match and you're pretty much screwed. Make sure you are using a small paintbrush with a pointy tip. First have the tip barely touch the groove, then as you move along the groove, lower the tip down into the groove making sure that the paint is not just applied to the groove, but also a bit out of its boundaries, since the rubber applied to the grooves of real tarmac is slightly wider than the groove.
Now for "used" look part, this is where it becomes tricky. Thin the paint you used for the grooves to about the same consistency of water. Using a big paintbrush put a little bit of the thinned paint on it. Now here is where the final decision is made. The wider spread you want your oil spills the higher you hold your brush. Now carefully shake the brush up and down to shake off the paint, if all goes well, you will achieve an nice tarmac with a few oil spills, If you know the position of you model on your tarmac, you can ad some extra oil spills to the area where your jet's engine bay will be when the jet is in parked position, or other heavily maintained areas (you get the idea). If by accident you do apply too much paint you should immediately wipe it off with the piece of paper towel that you have right there next to your project (hint, hint.) If this is not sufficient you may attempt sanding the cardboard with a very fine grid sand paper (600 and up, but be very careful with the sanded areas as they will tend to stain easier then the other areas).
But now your tarmac still looks quite new. This is because it is not discolored yet. Tarmac usually discolors into two different shades: brownish for an abandoned area of the airfield, or darker shades of gray for heavily used areas. This effect is quite easy to achieve, but also easy to overdo (as with weathering your aircraft). Since you are using cardboard you must use a dry powdery substance. Chalk pastels are excellent for this effect. Scrape some powder off the chalk so it falls onto the desired area (as this is one of the only ways to spread it out evenly). Experiment on a piece of scrap cardboard you have lying there and don’t forget to experiment with the color yellow and brown. It is very important not to touch the powder lying on the cardboard with you fingers as the slightest moisture can make these stains permanent; instead I found it useful to use a piece of felt wrapped around a solid object with a flat surface like a piece of plywood. Now carefully start to move the piece of felt over your surface (once again experimenting first) until the desired effect is achieved. If, by accident, it is overdone, you can try to use the sand paper technique for this, but it tends to have less of an impact then on the oil stains.
Now you have a nice piece of realistic looking tarmac.
But if you wish to add to the realism, you can add some grass with small stones and branches to the tarmac, making sure the grassy area has its boundaries at the grooves of your tarmac. I used "Woodland Scenics" (a railroad model company who specializes in the making of scale vegetation, and can be found in almost any hobby shop) coarse and fine turf in two different shades (very important). It is also important to add a third dimension to the grassy area, you can do this by gluing layers of cardboard on the surface and then adding the scale grass, this will make your diorama more dynamic. I also added some tall weeds, also from Woodland. For further detailed instructions, check out some model railroad magazines.
I discovered something that was easy to create and greatly improved the realism, put a small amount of glue on just a few intersections and straight areas of the grooves, just like you did to create the rubber, then sprinkle your scale grass onto it and you will have grass growing out of the tarmac grooves. Another area to apply this to is where the grassy area meets the edge of the tarmac. Apply it to the groove that meats with the grass perpendicularly, just make sure that the grass doesn’t extend too far down the grooves.
To finish off create a wooden frame of some sort to frame off you tarmac, and TA-DA! A fantastic looking piece of art that actually has a purpose.
Florian
Richard