[?] I read the recent FSM article and used tempera for panel lines against an Alclad polished aluminum finish. Unfortunately, this requires a sealer on the Alclad before doing the panel lines. Is there anyway to avoid having to seal over Alclad? Question 2: what’s the practice of good modelers when it comes to panel lines? paint 'em or not? Thanks!
Can’t help ya with the Alclad. Haven’t used them yet.
As for best… err… sorry consulting speak coming through… good practices on panel lines, I’ve done all of the following three things.
1) Pre-shade the panel lines by first spraying black or a shade of the color the primary color over the panel lines before applying the overall primary color. For example, a dark shaded olive drab (OD) like Tamiya OD is sprayed along the panel lines first, then a lighter shaded OD like ModelMaster Acryl OD is sprayed all over.
2) You could do the panel line shading last, but may need to tone down the darker shade with the lighter one. This is the approach I took with my B-25J “Emergency Strip” below.

3) See Swanny’s website for “The Basics of Weathering” (http://www.swannysmodels.com/Weathering.html).
All three work. I’ve used them on all different planes.
Jayzee,
A wash always looks good in panel lines…I try to avoid the stark black versus white look - on a white aircraft I’d use a mid gray or an oil paint wash to tone down the contrast and make it look a little more realistic.
Quagmyre suggests pre-shading - I agree, and it works really well - but if you plan on a multi-color cammo scheme, then the second or third color will make all that lovely pre-shading just disappear…bugger!
Many folks have stated that they use Tamiya Smoke to POST-SHADE their panel lines…and from their pics, it works very well.
On Alclad, I’d try to avoid using any wash that would damage the paintwork - maybe a Tamiya water based acrylic thinned with distilled water.
On an earlier post (search sealer on AlcladII) someone said they had used acrylic washes over alclad with no sealer and achieved successful results.
I like to use a finely sharpened drafting pencil using #2 lead and go over the panel lines LIGHTLY, so as to give just a hint of them being there. I don’t think the harshly contrasting lines are realistic in most cases. Something like the AD or A-1 Skyraider where that trusty ol’ R3350 radial was throwing oil all over the place is a different story. A coat of clear flat, (or gloss), goes over that to protect everything.
Darwin, O.F. [alien]
Alclad2 is a Lacquar and will stand up to just about any wash after it has fully cure at least 48 hours. If you are worried about about just use an acrylic paint that is dark gray thinned about 90% with water and a drop of dishsoap and use a fine brush to apply it directly to the panel line. The Dishsoap will help the wash come off the Alclad better… leaving the panel lines nice and gray.
Some good suggestions to work with here. Thanks to those who replied.
jayzee
Although it’s not panel lines, this is a wash over Alcad in the wheel wells and landing gear.
The parts were first sprayed with Future, rather than primer. I applied the Alcad (Aluminum, White Aluminum, Dark Aluminum), then sealed it with Future. The washes were done with enamels, mixing a dark gray (RLM 66) with a little black. The Future didn’t change the metallic look of the Alcad.

If you are using the Chrome or Polished Aluminum, I would suggest using the drafting pencil technique described by yardbird.
Hope this helps.
A varnish or sealer is good for a coat of any aluminium,but it will destroy the effects of panelling.
A nice way is to wash panel lines with varnish!!!
Give it some time to cure and wash again with regular black,grey or brown mixes.
You can also use a mix of pastels and water,tempera,ink, even a pencil…
Again here, the secret is TIME