1. A substantially alkali-free glass comprising in mole percent on an oxide basis:

SiO2: 65-70.3

Al2O3: 11-14

B2O3: 2-7.5

MgO: 2-7.5

CaO: 3-11

SrO: 0-5.5

BaO: 0-2

ZnO: 0-2wherein:

(a) [SiO2]+[Al2O3]?81.3;

(b) ?[RO]/[Al2O3]?1.3;

(c) a0+a1*[Al2O3]+a2*[B2O3]+a3*[MgO]+a4*[CaO]+a5*[SrO]?775

where a0=847.516, a1=4.747, a2=?10.144, a3=?5.089, a4=?6.837, and a5=?6.548; and

(d) a0+a1*[Al2O3]+a2*[B2O3]+a3*[MgO]+a4*[CaO]+a5*[SrO]?1310

where a0=1710.446, a1=?7.715, a2=?14.847, a3=?17.550, a4=?16.643, and a5=?12.574; andwhere [SiO2], [Al2O3], [B2O3], [MgO], [CaO], and [SrO] are the mole percents of SiO2, Al2O3, B2O3, MgO, CaO, and SrO, respectively, and ?[RO] equals the sum of the mole percents of MgO, CaO, SrO, BaO, and ZnO.